Monday, 19 December 2011

Happiest days of 2011: Tweeting reveals our daily mood swings

If you wanted to measure daily rhythms in activity of mice, you could record wheel running behaviour. If you wanted to measure daily changes in hormone levels, you could take regular samples throughout the day and night. And these days apparently, if you want to measure daily mood swings in humans, you can look at what words they are tweeting.

Twitter is a 5-year-old social networking website, claiming over 100 million users who are tweeting an average of 230 million tweets a day. Scientists this year have taken advantage of this free public access to our real time moods and have used tweets to analyse our daily, weekly, and seasonal mood swings.

Cornell researchers Scott Golder and Michael Macy analysed 509 million messages tweeted between 2008-10 from 84 countries [1]. These tweets were published online by 2.4 million English speakers that had written between 25-400 messages.

They measured positive words (agree, fantastic, super) which showed tweeters delight/enthusiasm/activeness/alertness as well as negative associated words (afraid, mad, panic) which reflected writers' distress/fear/anger/guilt/disgust. Then they looked for changes in the amount of positive or negative words over the day and across seasons.

Their first finding was that positive words and negative words have different rhythms, showing that these moods are not different ends of the same spectrum, but more complex.

They found daily mood changes: people are more positive early in the morning. This happiness dips during the day and then rises again in the evening. This daily mood swing also happens at the weekend, albeit 2 hours later (after a lie-in?) suggesting that work isn't entirely to be blamed for our daily dip in enthusiasm. However, overall people are happier at weekends when they don't have to work and can sleep when they like.

Our daily mood swings as analysed from 509 million "tweets" from 2008-10. Adapted from Golder & Macy 2011
One of the real strengths in this analysis is they also looked at tweets from those living in the United Arab Emirates, where the weekend is on Friday and Saturday. They observed the same weekend trend as we have in the West, where the weekend is Saturday and Sunday.

Larks (morning risers) and owls (evening types) who tweet at different times of the day also have different rhythms in positive and negative tweets [1.1].

Golder & Macy's final findings show that when the days are getting longer, we get happier, but when the days are getting shorter our positivity decreases. However, there are no seasonal affects of negative words, so the "winter blues" seem to be a net result of less positive thoughts rather than more negative ones.

A more recently published study of the happiness of tweets over 3 years, has produced an incredibly detailed picture of rhythms of tweets [2].  The daily peak for 'coffee' tweets occurs between 8 and 9 am. Outliers of our daily happiness can also be picked up: these occur on holidays, such as Christmas, and during global tragedies, such as the tsunami.
"Coffee" is most frequently tweeted between 8 and 9am
Twitter and social media sites are becoming an invaluable resource to scientists studying our social rhythms. The data is generated real-time with no reliance on memory. They provide a larger data set, representing the general public better than small groups of American undergraduates. However, like any questionnaire, they do rely on the emotions that people publicly share, rather than what might be their innermost emotions.

Overall twitter is helping to reveal humanity's mood swings, and the universal effect sleep and the body clock have on our mood.

[1] “Diurnal and Seasonal Mood Vary with Work, Sleep, and Daylength Across Diverse Cultures.” Scott A. Golder and Michael W. Macy. Science, Vol. 333, Sept. 30, 2011

[2] "Temporal patterns of happiness and information in a global social network: Hedonometrics and Twitter" Dodds et al., PLoS ONE, Vol 6, e26752, 2011

Monday, 12 December 2011

How a Poinsettia knows it's Christmas Time

Today, Monday 12th December, is National Poinsettia Day, yup there really is a day for everything in the US. Poinsettia, or Euphorbia Pulcherrima, flowers red during the winter season. It's star-like shape, representing the Star of Bethlehem, and it's blood-red colour, symbolic of Christ's blood, has made it a popular Christmas plant.

However, if you've kept a poinsettia throughout the year, you would notice that during the summer it is a white plant, and it's only when the days become shorter that it develops it's redness.

The Poinsettia flowers red at Christmastime (C) bourgeoisbee
How does the poinsettia know when to flower red? Is it counting the number of days throughout the year? Or does it count the number of hours of daylight each day? In fact, it's neither of these, but down to it's internal clock...

The poinsettia is a short-day plant, requiring a long period of darkness to flower. A lot of the experiments to understand when plants flower have been done on long day plants such as Arabidopsis. These plants need a long period of light in the day to flower (usually >12 hours) and a short night.

The chemical that absorbs light is called phytochrome, this can exist in two forms. The "red" form, PR, which absorbs light during the day, and the "far-red" form, PFR, that is converted from PR during the night when there is no daylight.
Phytochrome is the chemical in the plant that absorbs light which converts it from the Red to the Far Red form

During the day PR is produced by daylight. During the night all the PR is converted into PFR, this only takes 2 hours to complete. If you expose a long-day plant to pulses of light during the night, it can trick it to thinking the day is long and it's time to flower. If the plant were merely counting the number of hours in the day, this wouldn't work.

The longer hours of light allow for the accumulation of PR alongside the protein Constans (CO), which initiates flowering. CO is controlled by the plants internal clock, so it has low levels during the day, and only rise during the late afternoon if there is enough light and PR. In order to flower the Arabidopsis requires both daylight to be detected by phytochrome, and the circadian rhythm of CO.

Understanding how short day plants work was a bit more tricky. But genetic studies on the short day plant rice are beginning to reveal that the clock in short day plants effect the same genes, but they have opposite effects on the plant [1]. So in a long day plant genes that activate flowering in a short day plant inhibit flowering.

Other short day plants include the tobacco plant, strawberries, and chrysanthemums.

I hope you enjoy celebrating National Poinsettia Day with a greater appreciation of the seasonal colouring in these short day flowering plants.

[1] "Genetic Control of Flowering Time in Rice, a Short-Day Plant" Yano, M et al., Plant Physiology, vol. 127 no. 4 1425-1429, 2001

Monday, 5 December 2011

Double summertime: Double trouble? Part 3

In this third blog post about single double summertime (SDST) I will respond to some of the supposed health benefits advocated by supporters of the lighter later campaign.

Dr Mayer Hillman, an active advocate of SDST, has predicted health benefits including, lighter afternoons might encourage more outdoor leisure pursuits leading to a reduction of obesity and related disorders[1]. 

However, these are assumptions on behavioural habits and there is currently no scientific evidence to support that an extra hour of light in the afternoon will be sufficient to increase outdoor exercise in the UK population. For those in London during winter the sun will set before 5pm, not significantly lengthening the daylight leisure time (map showing changes).

Will an extra hour of daylight encourage more outdoor exercise?  (c) Jon Candy
Hillman also suggests people will be exposed to more hours of daylight and are therefore likely to have improved mental wellbeing, more energy and lower rates of sickness. However, SDST will not increase the number of hours of daylight: it will only shift the timing of daylight hours to later in the day. In fact, deprivation of morning daylight is likely to cause the opposite effects: depression, sluggishness and higher rates of Seasonal Affective Disorder, SAD.

SAD, sometimes called the "winter blues", is thought to affect 2 million people in the UK. SAD in its most severe form can be debilitating, rendering sufferers unable to function during winter without treatment. It is often treated successfully with light therapy alone. The most successful treatment is morning light exposure from daylight imitating lamps, and is effective with over half of patients not requiring any other type of treatment[2]. This highlights how important quality, quantity and, crucially, timing of light is to our biology.

Lamps that simulate dawn are effective at combating SAD (C)  Susannah
In 2011 medical professionals at the British Medical Association annual conference rejected a bid to support SDST. There was a lack of categorical evidence for the supposed health benefits.

To achieve a healthier society, with increased productivity and performance, we need to encourage better synchronised body clocks. The health consequences of exposing ourselves to unnatural lighting conditions are being unravelled. Unnatural daylight hours are likely to intensify these detrimental consequences. 

Giving the proven importance of light in the morning on health, a policy that reduces morning daylight should not be supported on health purposes.

2.          Terman, M. & Terman, J.S. Lighttherapy for seasonal and nonseasonal depression: efficacy, protocol, safety,and side effects. CNS spectrums 10, 647-63; quiz 672 (2005). 

Wednesday, 30 November 2011

Double summertime: Double trouble? Part 2

To determine whether we should the UK should have single double summertime (SDST) in the UK in this second blog post I will review large-scale trials of SDST. What effect that has had on the population health? I will also look at evidence comparing people in the same time zone: those living in the west, where the sunrises later in the day. Can the time of sunrise really impact our health?

Interpreting data over large scale trials is hard to establish, due to the amount of factors involved.When SDST was trialled in the UK between 1968-71 Parliament were unable to determine any clear benefits and reverted back to Britisth Summer Time.  One of the factors they were looking at was the rate of road traffic accidents. However, the introduction of a legal drink drive limit in 1967, and the first roadside breathalyser in 1968, made it difficult to determine the influence of SDST in the reduction in road traffic accidents. 

Breathalyser and the Drink Drive Limit reduced road traffic accidents in the late 1960s, obscuring any positive effects directly from the SDST trial (C) Isabelle Adam
Portugal, who are currently on the same time zone as Britain, moved to SDST in 1992, and soon moved back in 1996. SDST was unpopular in Portugal, despite the advantage of being on the same time zone as neighbouring Spain.

Portugal noticed the fall in children’s exams rates. The later light in the evening made it harder for the children to sleep, getting few hours sleep each night and causing their grades to fall. In my opinion, reduced performance at work would be a risk for most age groups, however children’s grades are the easiest to measure.

The Daily Mail reported that Portugal during SDST had an increase in insomnia, sleeping pill usage, and stress levels.

Will SDST increase sales of sleeping pills? (C) pinprick
The time of sunrise also impacts winter depression. Dr Michael Terman, an expert in circadian timing and depression, has researched the rates of winter depression in the US. He studied 5114 persons aged between 18-60 over 3 years across the US. His findings indicate that people further North, who receive less hours of daylight, are more prone to the "winter blues".

There's not a lot policy can do about the number of hours of daylight, but interestingly, the time of sunrise in this trial was also an important factor. Those living in the western edge of a timezone above 38 °N, where sunrises later than the eastern edge, have 26% more cases of winter depression[1].

The UK lies 50-60 °N, and this data provides a strong case for the UK not to enforce a later sunrise, and for further investigation to determine how the time of sunrise effects cases of winter depression in the UK.

The current bill requires a review of the success to be established; the effects on health such as rates of sleeping disorders and depression, sale of sleeping pills, should be clearly assessed as part of this. Also, research should be undertaken to understand the relationship between time of sunrise and rates of winter depression in the UK, before changing it.

[1] "Predictors of winter depression: latitude and longitude in relation to photoperiod and sunrise"
Terman, et al, Soc Light Treatment Biol Rhythms Abstracts 2008; 20:56

Tuesday, 15 November 2011

Double Summertime: Double Trouble? - Part 1

This year MP Rebecca Harris has proposed the Daylight Saving Bill. This bill requests a 3 year trial of advancing the clocks by one hour for the entire year. This has been termed “single double summer time”, SDST, and will result in the UK being one hour ahead of GMT during winter, and two in summer. Many social and economic factors have been discussed in the media and Parliament, however the impact on the circadian system, or body clock, has received less attention.

This is quite a large topic, which I’ll deal with in a few blog posts. In this post I will review why light in the morning is important for our body clock. In the second blog post I will review other trials that have tried shifting time zones, and what effect that has had on the population health. Finally, in the third blog post I will respond to the supposed benefits advocated by supporters of SDST.

Light in the morning is the strongest time cue to synchronise our internal body clock with the environment. Our internal clock is responsible for synchronising many bodily functions, including the sleep/wake cycle, metabolism, appetite, digestion, alertness, cognition, athletic performance, blood pressure, body temperature, sex-drive, body repair, energy get the idea?

Common examples of a desynchronized body clock are seen in shift workers, travellers with jet-lag and sleep disorder sufferers. You will probably even notice this desynchronisation after pulling a few late nighters. A healthy body clock is vital for a healthy body and mind.

Light in the morning provides the strongest cue to sync our body clock with the day (C) jozerC
The influence of light on the human body clock has been widely investigated using bunker isolation units, blind people, and large scale studies. These studies show how our body responds to same amount and type of light differently at different times of the day. 

Bright light in the evening, a result of SDST, delays our body clock. This delay can cause us to need to sleep later, and when we still have to wake up at the same time, can cause ‘social jet-lag’.

Light can also directly affects our hormones, in particular suppressing melatonin production within 20 minutes of light entering our eyes. Melatonin is produced from the brain at night and induces sleepiness. A lack of morning daylight increases the duration of melatonin production, causing sluggishness and inattentiveness.
Key brain regions involved in circadian timekeeping. The brain receives light input from the eye, and uses this signal to co-ordinate time of day information to the rest of the body.

Light at night, which is increased during the summertime with SDST, disrupts our body clock even further. Dr Malcolm von Schantz, an expert in circadian rhythms and sleep research at the University of Surrey, has voiced concerns that light later into the evening can result in poorer sleep quality and less sleep than required. SDST will result in areas in Scotland not having sunset until 11.30pm during summer

It is not sufficient to just count the number of daylight hours, the timing of these hours needs to be considered.

Thursday, 3 November 2011

The SCN Song

On the 1st Nov 120 people gathered in a pub to watch the second Science Show-Off, an evening of acts from Scientists explaining their science in an entertaining manner. Adam Strang told us why chillis taste "hot", and gave us a demonstration as he preceded to eat 5 in increasing "hotness". Suze Kundu made ice cream from custard and liquid nitrogen to explain the different states of matter. And my personal favourite, I'm entirely biased here, was my lab partner Catherine Cox's song on the SCN with a ukelele.

Catherine singing the SCN song (c) Katherine Belessiotis
This was Catherine's debut performance on the ukelele, and from the audience reaction it was a resounding hit.

Catherine's song is all about the suprachiasmatic nucleus (SCN), the master clock in the human brain. The SCN is a brain region that co-ordinates and synchronises all the daily biological rhythms in our body. It has direct connections with the eyes so can be re-set by light, otherwise we would never get over jet-lag!

Here is a video of the performance, sorry we didn't get good enough visual, hopefully you'll enjoy the lyrics! I think the audience did great, especially without any practice!

Thanks Catherine for this amazing contribution to the education and communication of body clocks!! For those of you interested in attending (or presenting) at a Science Show Off event please visit:

Wednesday, 2 November 2011

Running the Venice Marathon 2011

I haven't written a sciency blog post for a while, and the reason for my absence (besides the PhD) is that Simon and I have been spending our evenings and weekends training for the Venice Marathon. I'm so pleased that all those months and late night runs paid off, we both finished mostly-injury free, and had the most amazing experience doing it!

We decided to take on this crazy endeavor to raise money for the Royal National Children's Foundation. Thank you so much to everyone who has donated, there's still time to contribute here.

The Sunday morning of the race started at 6am with a quick breakfast and off to get the bus to the start. We had been advised to get the 3 min shuttle to Tronchetto, inventively named the "People Mover". When we arrived it was closed, but was going to open early at 7.10 for the marathon, however the last bus would have already left. A bit of a fail on the organisation, this wasn't boding well.

We joined the crowds and walked over to the bus stop. It was still before sunrise when we huddled onto a crowded bus for the long ride to the start, it felt like we were going in the wrong direction - away from Venice. When we arrived at the start it was still very cold, and I felt I was already being brave just taking my coat and trousers off to them on the truck - why were we doing this?

An hour later we crossing the start line, the sun had come up and there were brilliant blue skies. We soon started to warm up on the run. The route was idyllic, running alongside the Brenta River through small towns with great crowd support.

Early on in the race, struggling to get into a pace, but enjoying the spirit of the runners
We were sticking with the blue balloons for the 4hr30 pacemakers for several miles, but then had to do a quick toilet stop and never managed to catch up with them again. At 12 miles I was struggling, I felt I still hadn't got into a good rhythm (this had been taking longer the longer our training runs had gotten). I took some ibuprofen, gels and water, and gave the rucksack to Simon, and started singing an awesome running song.

By the half way point I was feeling much better and running through Mestre at mile 16 I was feeling amazing. I was finally in the "zone", the crowd support was amazing, and my legs were feeling great - we could finish this! Mestre had been described in the guidebook as Venice's ugly sister...I felt this was completely unwarranted, the streets were beautiful to run through and I was really enjoying this.

Awesome crowd support in the local towns, this was Mestre, Venice's not-so-ugly sister
The rest stops were now supplying awesome Italian cookies and fruit as well as Gatorade and water. They were all well stocked. My feet were definitely blistered and it really felt as though I'd lost a toenail (I hadn't).

Running through San Guiliano Park at 18 miles we were surprised to hear one of the bands singing Shinedown's Simple Man - how amazing!! We love this band and especially this song, there had been lots of rock bands dotted along the route, and it's so uplifting when you hear a song you love. We were going to need this for what was to come.

Liberty Bridge. How ironic. This is the 4km long bridge that stretches on for eternity. Connecting Venice to the mainland running onto this bridge you get your first glimpse of Venice, very exciting for the first time. However, after 30 minutes of running and Venice isn't getting any bigger you get to the point of despair.

We were very grateful when we did arrive in Venice that there would be only 3 miles left of the course to do. We reached the first bridge and saw the small sign "14 bridges to go". No bridges, no fun!

No bridges, no fun! Running in Venice, with the Santa Maria Salute in the background
At 38km I had a sharp pain in my left leg, and could I get this close to the end and then be injured! I spent 20 seconds walking and massaging it and then pushed on with the running, we were putting every bit of effort into running this race, and nothing was going to stop us pushing ourselves to the limit. No one would say that we didn't put everything into this race. We were going to achieve this. Pain is temporary, glory is everlasting!

Running into San Marco Square was electric. People were calling out our names, the Basilica and architecture was overwhelming, it was everything I could do not to cry! I could not wipe the large smile off my face, all these months of training were paying off, and Simon was beside me the whole way!

Running around San Marco Square!

Running hand-in-hand, the crowd support in here was electric!
The last 1km was frustrating, 5 more bridges to go and that finish line was still not in sight. The crowd were so impressive, they really kept us going. Finally, the last bridge and we could see the finish line, I told Simon we were going to sprint through, he was not impressed, but I'm not sure he had the energy left to complain. We put up our arms and the 4 hour 39 minute time was ours!!

Crossing the Finish Line

Our actual time (minus how long it took us to get to the start) was 4 hour 39 mins! Woo!

Simon very relieved it's all over
Thank you to everyone who has supported us and the RNCF charity. It's been a lifetime achievement for both of us and I'm so grateful for Simon sticking with me and doing this - I love you!

Space blankets and medals! There was also pasta, what a great incentive to finish!

Our official finishers photo


Tuesday, 26 July 2011

Around the Clock Doc

On the bus this week there was a poster advertising "around the clock" access to an NHS GP to the residents of Lambeth & Southwark. We are lucky in the UK that we can have access to health services at any time of day or night, which is great for when emergencies arise.

Free access to emergency healthcare information: NHS bus advert to patients in Lambeth & Southwark
However, are GPs making full use of the "time-of-day" information in their diagnosis of disorders?

Last Summer I went on a fascinating Chronobiology course in Germany where we studied how the time of day can affect biology.

One of the parts of the course involved wearing a portable blood pressure monitor that monitored my blood pressure every hour over the course of a day and night. It was a bit annoying having this contraption on my arm, but I did manage to stay focused in the lectures and get some sleep at night time whilst wearing it.

The results were really interesting. There was a clear daily rhythm in my blood pressure, dipping low at night and rising again during the day.

I was also classified as a "white-coat hypertensive", i.e. I had high blood pressure at the start and finish of the recording, when I knew someone was monitoring it. So I know in future to be careful not to be mis-diagnosed as hypertensive at the doctors.

It is normal for your blood pressure to dip at night, whether or not you are sleeping at the time. But some cardiovascular problems cause your blood pressure to remain high at night, in this case, it's better to take your blood pressure medication before going to bed. However, if your blood pressure does still drop at night normally, then it's better to take this medication in the morning, when the blood pressure will be rising.

Your circadian profile of blood pressure can help a doctor diagnose any problems, and indicate which treatment is best for you
There was one case our lecturers were relating to us about a person who was feeling really ill. When they monitored his circadian blood pressure profile they could see his blood pressure dipped dangerously low at night, and the medication he was taking just before bed was making it dip even lower.

Portable blood pressure monitors are expensive but the results can really help with diagnosis of cardiovascular problems. Blood pressure is a clear example of how our body changes over the course of 24 hours, and how by monitoring and understanding this condition we can improve our health services.

Sunday, 17 July 2011

Jet lag

July is with us, and with it the Summer holidays, the season for travelling abroad. For some of us, that’ll mean travelling across many time zones that confuses our body clock and causes “jet lag”.

Our ancestors didn’t have to worry about “horse-and-cart-lag” or “boat-lag”, but due to the advent of high speed flight we can put our body in a different time zone very quickly.

Our ancestors didn't have to worry about the effects of crossing time zones quickly on their body clock. Image (C) Jungle_Boy

When we suffer jet lag, the rhythms of our different organs become out of sync with one another. Our stomach wants food at the wrong time; we are wide awake at night and sleepy during the day; our hearts have low blood pressure during the day when we are being active.

To top this off we can suffer symptoms from flying itself: dry mouth from the air conditioning, cramped muscles from sitting still for so long, tiredness from not sleeping well.

To maximise the fun we have on holidays I have provided some tips to minimise the effects of flying and to resynch to the new time zone as quickly as possible.

To prevent the short term effects of flying, and this includes when flying northerly or southerly where you won’t change time zones, follow these tips:

1. Drink plenty of water, and less caffeine, carbonated drinks, and alcohol.
2. Walk around on the plane and do regular leg exercises. Loosen or take off your shoes.
3. Plan your trip to arrive in the evening, this way you can sleep off the travel fatigue when you arrive.

Strategies to adjust your body clock rapidly to the new time zone depend on whether you are flying East or West. When going East you need to wake up earlier, this effectively shortens the day. When going West you need to stay up later, effectively lengthening the day. Most people’s body clock runs slightly longer than 24 hours, so it’s easier to stay up later, and therefore westward travel can be quicker to adapt to.

If anyone can think of a better pneumonic for westward travel being easier - let me know! (C)  Helen Moore, 2010

In the days before you travel:

Eastwards travel (2 timezones or more):
1. Go to bed earlier, and wake up earlier. Try and get plenty of sleep and rest.
2. Eat your meals earlier. Have a good meal before your flight.
3. Exercise in the morning.

Westwards travel (3 timezones or more):
1. Stay up later, and lie-in in the morning. Try and get plenty of sleep and rest.
2. Eat your meals later. Have a good meal before your flight.
3. Exercise in the afternoon.

When you arrive at your destination:
1. Work your schedule according to the local time zone.
2. Set your alarm clock.
3. Exercise in the morning, preferably outside (even a 30-min walk will help).
4. Expose yourself to bright lights in the morning, and dim lights in the evening (wearing dark sunglasses in the evening can help).
5. Have some fruit or sugary snack by your bedside to suppress night-time hunger – no caffeinated food (including chocolate).
6. Don’t have caffeine within 5 hours before bedtime.
7. Take a 20 minute powernap in the afternoon if you are struggling to stay awake.

Tuesday, 28 June 2011

Breast cancer and the seasons

Following on from my research on annual body clocks last week, I came across quite a number of papers associating the season of detection of breast cancer with survival rates.

A 7-year study that was published in 1983, looking at ~3000 female patients showed a peak of breast cancer symptoms in Spring, with a corresponding trough in the Autumn [1]. This has been verified in many other studies across the globe, showing tumour growth and aggression is higher in Spring.

Larger studies went on to determine a link between the survival rate of cancer patients and the seasons the tumour was detected and treatment began. One study of over a million cancer patients in the UK showed that a patient diagnosed in the Summer or Autumn had a greater chance of survival than if diagnosed in the Winter [2].

A smaller study, under 50 000 women, in Norway also confirmed that a Summer diagnosis increased the chance of survival by 10-15% over a Winter diagnosis [3]. This data was collected between 1964-1992 and looked at the differences in age and the region them women were living. Women under 50 that lived in a region with more sunlight had a better prognosis than those regions with less sunlight. However, although seasonal rhythms were detected, no regional differences were observed, in women over 50.

Women (under 50 years old) in Norway had a lower risk of dying from breast cancer within 3 years if their detection and treatment began in the Summer, in a region with most sunshine. (Porojnicu et al, 2007)

So, can sunlight improve survival rates of breast cancer? Or are there other factors, such as a higher number of infectious diseases around wintertime.

There is growing support that vitamin D, a chemical our body makes in response to sunlight, plays a role in survival against cancer [2]. Lab studies have shown that the products our body makes from vitamin D slow down cell growth [4]. Also, seasonality in cancers is more likely to be seen in women than in men, which is consistent with women being frequently reported of having lower vitamin D levels in winter.

One way to look at the link between vitamin D and cancer would be to look at cultures that eat more dietary vitamin D, or have a diet that changes the rate of vitamin D production. Drug companies are also looking into producing the products of vitamin D that may help cancer patients.

The link between vitamin D products and cancer survival still needs to be fully addressed. Until then, the advice is for women to check themselves monthly, and go out and enjoy the summer sunshine. (Don't forget the sunscreen!)

[1]        P. Cohen, Y. Wax, and B. Modan, “Seasonality in the occurrence of breast cancer.,” Cancer research, vol. 43, Feb. 1983, pp. 892-6.
[2]        H.-S. Lim, R. Roychoudhuri, J. Peto, G. Schwartz, P. Baade, and H. Møller, “Cancer survival is dependent on season of diagnosis and sunlight exposure.,” International journal of cancer. Journal international du cancer, vol. 119, Oct. 2006, pp. 1530-6.
[3]        A.C. Porojnicu, Z. Lagunova, T.E. Robsahm, J.P. Berg, A. Dahlback, and J. Moan, “Changes in risk of death from breast cancer with season and latitude: sun exposure and breast cancer survival in Norway.,” Breast cancer research and treatment, vol. 102, May. 2007, pp. 323-8.
[4]        C. Hansen, L. Binderup, and K. Hamberg, “Vitamin D and cancer: effects of 1, 25 (OH) 2D3 and its analogs on growth control and tumorigenesis,” Front Biosci, vol. 25, 2001, pp. 820-848. 

Tuesday, 21 June 2011

The Longest Day of the Year

Today, the 21st of June, is the longest day of the year, commonly known as the Summer Solstice. The sun will be in the sky for 4 seconds longer than yesterday and 2 seconds longer than tomorrow. But more importantly, in the UK Summer has now officially started, and surprisingly we have blue skies and sunshine in London.

Blue skies in Greenwich at Summertime

I thought I’d take this opportunity to read up on and discuss whether our body has an annual clock, as well as a daily clock.

To measure the time of year, an animal can either know it is Winter, because the daylength (exposure to light) is short, or it can have an innate clock inside that measures one year. Or it can have both.

In some species annual clocks are very apparent: in Autumn birds begin to migrate to warmer climates, in Winter bears hibernate, in Spring lambs are born and in Summer we see our garden plants flourish.

There is much less research carried out on annual rhythms as opposed to daily rhythms. It takes scientists much longer to collect the data, and there are many variables that can cause any observed rhythms, which makes the data harder to interpret.

In humans it is especially tricky. Length of daytime is not the only thing that alters during the seasons. There are potential effects of temperature, climate, food availability, agricultural cycles, and holiday seasons, to name but a few.

One study has looked at the quality of embryos and sperm produced for IVF treatment in Iranians between June 2001 - June 2004, which included over 1000 treatment cycles [1]. They showed conception was much more likely during the Spring months of March-June.  This time was also the best for quality of embryos and men had a higher sperm count. However, no changes were observed in egg number, sperm quality, and other factors.

Seasonal effect on number of successful pregnancies following IVF treatment  in different seasons,  (Vahidi et al, 2004)

Has electric lighting, and the ability to have as long or short a daylength as we like, disrupted our annual clock?

Another investigation published in 2004, examined the birth patterns in Spain between 1900-1978 [2]. Up until the 1960s there was a strong correlation between season and birth. However, when industrialization and subsequent changing in heating and lighting conditions was introduced the amplitude of this rhythm dropped: there wasn’t such a difference observed between different seasons.

The question whether humans still have, or if we ever had, an annual clock of changing biology and behaviour is still open for a lot of research and debate. Russell Foster, a researcher at Oxford, has written an interesting and in depth book on annual body clocks, which I would recommend to anyone who enjoys this topic.


[1]        A. Vahidi, S.M. Kalantar, M. Soleimani, M. Hossein, A. Arjmand, A. Aflatoonian, M.A. Karimzadeh, and A. Kermaninejhad, “The relationship between seasonal variability and pregnancy rates in women undergoing assisted reproductive technique,” Iranian Journal of Reproductive Medicine, vol. 2, 2004, p. 82–86.

[2]        T. Roenneberg, “The decline in human seasonality.,” Journal of biological rhythms, vol. 19, Jun. 2004, pp. 193-5; discussion 196-7.

Monday, 13 June 2011

Red sky at night, sleepers delight!

Ever been camping and felt really sleepy and time for bed, only to discover its just 8pm?

How about staying up til 2am playing computer games (perhaps later?) because you didn't feel tired.

Do you struggle to get out of bed when the alarm clock rings in the morning?

Hitting the snooze button isn’t always a sign of laziness; sometimes our body clock becomes out of sync with the outside world. Electronic lighting, TVs and computer screens are often pinpointed as the culprits for this desynchronisation.

Light is one of the strongest time cues to tell your body it's daytime. Simply put: light in the morning wakes you up, dark in the evening helps you fall asleep. Although it's not always as simple as that. The type and amount of light matters too.

Our body clocks are most sensitive to blue light. There are specific photoreceptors in the eye, at the back of the retina, that detect light and signal this to the brain [1]. These photoreceptors are particularly sensitive to shortwave lengths, i.e, blue, light.

Short wavelengths of 420-480nm (blue light) are most efficient at resetting our body clocks.

The circadian system is important to our biology so other wavelengths of light can still reset our clocks, but they need to be brighter. If you don’t want to stay up all night avoid bright white lights in the evening [2].

The photoreceptors are not sensitive to short bursts of light, so a single bolt of lightning would not reset your clock; the light needs to hit the retina for several minutes. So a long trip to the bathroom in the middle of the night might trick your clock.

If you want to get a good night’s sleep, in the evening use dim lights with longer wavelengths (reds) of light. A few computer users have found using software like f.lux useful. This is a free software that colours your computer screen in a red hue in the evening and night time. This is good news for those of us who still want to play on the computer in the evenings, without keeping us up all night. It comes on automatically, however it's easy to turn off and on for doing colour sensitive photographic work.

I’ve joined 46 000+ others in “liking” f.lux on facebook. If you do try f.lux, let me know how you get on.


[1]       T. Liesegang, “How the Brain’s Clock Gets Daily Enlightenment,” Science, vol. 295, Jul. 2002, p. 955.
[2]       J.J. Gooley, K. Chamberlain, K. a Smith, S.B.S. Khalsa, S.M.W. Rajaratnam, E. Van Reen, J.M. Zeitzer, C. a Czeisler, and S.W. Lockley, “Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans.,” The Journal of clinical endocrinology and metabolism, vol. 96, Mar. 2011, pp. E463-72.

Tuesday, 7 June 2011

I'm allergic to the morning

Summer is on its way, and for 1 in 3 of us this will mean hayfever too. I haven’t suffered from hayfever for a few years, although I do sneeze quite a lot throughout the year, and this is mainly when I wake up in the morning. It appears I’m not alone.

Two medical school students monitored the sneezing patterns of one of their classmates. The majority of their sneezes occurred at around 8.20am, and this shifted by 1 hour when daylight savings came on. After recording 118 sneezing episodes over the course of half a year, they admitted to their colleague what they had been up to and asked permission to publish their results [1].

A larger study of around 800 hayfever suffers has also showed that symptoms are most severe in the early morning. Around 60% suffered from sneezing, stuffy nose, blocked nose and runny nose when they woke up, and there was a clear daily rhythm of these symptoms [2].

Most hayfever sufferers show a daily peak in symptoms upon waking up (Adapted from Reinberg et al, 1988)

Hayfever symptoms are part of the immune system responding to an allergen, in most cases pollen. Histamine is one of the key chemicals produced by your body to communicate this response around the body. When the immune system is activated it produces a lot of histamine. Histamine interacts with the H1 receptor in the nose, causing inflammation to remove the allergen.

Antihistamine medication can relieve the symptoms of hayfever by reducing inflammation in the nose. However, the same H1 receptor that histamine interacts with is found in the posterior hypothalamus in the brain, where histamine plays another role in maintaining alertness. Early antihistamine medication often caused drowsiness by also interacting here.

It is often recommended to take antihistamines at night to counteract drowsiness during the day. If you are taking a once-a-day antihistamine tablet it is also advised to take it in the evening so the dose is being most effective in the morning when you wake up and it’s most needed [3].

It would be great to hear from any other morning sneezers.

[1]        A. C Grant and E. P Roter, “Circadian sneezing.,” Neurology, vol. 44, 1994, pp. 369-375.
[2]        A. Reinberg, P. Gervais, F. Levi, M. Smolensky, L. Del Cerro, and C. Ugolini, “Circadian and circannual rhythms of allergic rhinitis: an epidemiologic study involving chronobiologic methods.,” The Journal of allergy and clinical immunology, vol. 81, Jan. 1988, pp. 51-62.
[3]        M. Smolensky and L. Lamberg, The Body Clock Guide to Better Health, Holt Paperback, 2000, p260-5 

Monday, 30 May 2011

Nocturnal asthma

went down with a cold last week, the first day I was up at 2am all bunged up, coughing, and struggling to breathe. As I was sleepily sipping on my hot lemon and honey I remembered that I'm not alone - a lot of people have breathing difficulties at night.  In fact, I'm really lucky that I do not have asthma, as most asthmatics have a lot of difficulties breathing during the night. A survey of 7729 asthmatics in the 1980s showed that 94% had woken up in the night at least once in that month with difficulty breathing [1].
Many asthmatics have to take preventative medication before bedtime 
(c) Luke Morgan 2011

What causes this nocturnal asthma? Is it caused by our sleeping environment, or is there something innate about our body clock that intensifies breathing difficulties at night?

Our sleeping environment can make things worse. Allergens on our pillows (or teddy bears) can cause asthma attacks, even up to four days after contact. Then there's our position when we're sleeping, lying flat compresses our airways making it harder to breathe. Even cold bedroom temperatures have been known to trigger asthma attacks.

However, asthma is a textbook example of how the time of day affects our physiology. There are daily changes in many body rhythms that make breathing between the hours of midnight and 8am much harder. Two important hormones involved in healthy airway maintenance are cortisol and adrenaline. 

During the day adrenaline relaxes the muscles around the airway and cortisol reduces swelling, making breathing easier. At night, our body releases lower levels of both of these hormones, causing airway muscles to constrict and swell. This makes breathing at night harder. 

Daily changes in cortisol and adrenaline in healthy individuals at rest, adapted from Sheer, 2010 [2]

The implications of this hormone change in normal people causes a detectable, but low, amplitude change in the day/night variation of airway function. However, in asthmatics the the rhythm in airway function has a greater amplitude, making them more vulnerable to breathing difficulties at night [3].

One way to measure our lung capacity is to record peak flow. The higher a person’s peak flow the better their lungs are. One study in 1980 looked at the peak flow of normal and asthmatic sufferers throughout the day and night [4]. In the afternoon and early evening the peak flow was the highest in both normal and asthmatics. However, the asthmatic sufferers had far lower peak flow measurements during the night: a 50% difference in their best and lowest peak flow compared to only 8% in a non-asthmatic.

Asthma does not occur randomly over a 24 hour period, it is much more likely to attack during the night in most sufferers. There is still a lot to be investigated about the causes and types of asthma attacks that occur during the night. However, if you are constantly bothered by nocturnal asthma attacks, speak with your GP. By ensuring your asthma medication protects you during the night, you can avoid attacks and get a better night’s sleep.


[1]    M. Turner-Warwick, “Epidemiology of nocturnal asthma,” The American Journal of Medicine, vol. 85, 1988, pp. 6-8.
[2]    F. a J.L. Scheer, K. Hu, H. Evoniuk, E.E. Kelly, A. Malhotra, M.F. Hilton, and S. a Shea, “Impact of the human circadian system, exercise, and their interaction on cardiovascular function.,” Proceedings of the National Academy of Sciences of the United States of America, vol. 107, Nov. 2010, pp. 20541-20546.
[3]    M. Smolensky and L. Lamberg, The body clock guide to better health, Holt Paperback, 2000
[4]    M.R. Hetzel and T.J. Clark, “Comparison of normal and asthmatic circadian rhythms in peak expiratory flow rate.,” Thorax, vol. 35, Oct. 1980, pp. 732-8. 

Tuesday, 10 May 2011

Pimm’s all around the clock. Alcohol and Body Clocks Part 2

Chatting to a scientist at a party

When at a party and asked about body clocks alcohol is a great example to explain how our bodies respond to drugs differently at different times of the day (and no-one wants to be stuck talking to a scientist who doesn't have fun facts about their research). In Part 1 I've explained how our body clock can change how we respond to alcohol, but the same also works in reverse: alcohol affects our body clock with both short-term and long-term consequences.

Alcoholics often suffer from mood and sleeping disorders, and this could be exacerbated by how their own body clocks are damaged by chronic alcohol abuse.

Scientists look at the hormone melatonin to monitor body clocks. Melatonin is normally released only at night, and can be measured from urine samples, so it is a good and reliable indicator of an individual's clock time. In chronic alcoholics, their melatonin secretion is completely reversed: they produce it during the day! [1]

Melatonin rhythms are not affected in non-alcoholic healthy adults that drink alcohol [2], however, alcohol can still have a short-term disruption on body temperature rhythms. Normally, there is a 24-hour change in our core body temperature, dipping to its lowest of 36°C at 4am, and peaking during the day at around 37°C. Our body tries to keep to these temperatures by sweating when it's hot and shivering when it's cold etc.

Alcohol is thought of as a hypothermic agent, it makes your body cold, and hypothermia is an indicator of alcohol toxicity. Oddly however, taking alcohol at night time (when you should be asleep) raises body temperature. Drinking alcohol can change your body temperature's 24-hour profile.

A study was done on 9 healthy, non-alcoholic males, who had the arduous job of lying in bed all day and hourly either taking fruit juice or fruit juice and ethanol (to try and make it so they wouldn't know which they were taking). Their core body temperature was measured every 20 minutes (the old-fashioned rectal way), and it clearly shows that alcohol during the day lowers body temperature, but at night alcohol raises body temperature [3].

Alcohol changes the body clock's 24 hour temperature profile. Adapted from Danel, 2001

This is an excellent example of why a drug should be tested for its effects on the body with a complete 24 hour profile, not just seeing what its effect is during the day. For users, it warns us to be careful when drinking during the early hours, or even when our body thinks it's the early hours of the morning, such as shortly after a transmeridian flight. The effects of alcohol are not the same during the day and the night.

To sum up: body clocks can alter how we can tolerate alcohol, but alcohol in turn can alter our body clock.

[1]    G. Murialdo, U. Filippi, P. Costelli, S. Fonzi, P. Bo, A. Polleri, and F. Savoldi, "Urine melatonin in alcoholic patients: a marker of alcohol abuse?," Journal of endocrinological investigation, vol. 14, Jun. 1991, pp. 503-7.
[2]    T. Danel and Y. Touitou, "Alcohol consumption does not affect melatonin circadian synchronization in healthy men.," Alcohol and alcoholism (Oxford, Oxfordshire), vol. 41, 2006, pp. 386-90.
[3]    T. Danel and C. Libersa, "The effect of alcohol consumption on the circadian control of human core body temperature is time dependent," Am J Physiol Regul Integr Comp Physiol, 2001, p. R52-R55.


Tuesday, 3 May 2011

Pimm’s o’clock: Alcohol and the body clock Part I

Lunchtime drinking

Our bodies can tolerate alcohol better in the early evening. A pint at lunchtime will make you feel drunk faster than the same pint taken later in the day.

In 1941 the first link to alcohol was reported in the scientific literature, this paper showed that alcohol was removed slower from the body during sleep. [1]

Then in 1956 results showed that the metabolism of alcohol, how it is broken down, was affected by the body clock [2]. 5 lucky test subjects drank whiskey hourly for 2 days whilst the amount of alcohol in their blood and saliva was tested. There was a clear change in how fast their bodies were breaking down the alcohol so it could be removed from the body.

Many further experiments were carried out in the 1960's to 80's confirming these results, one can only imagine they had plenty of undergraduate students signing up as trial subjects.

Alcohol drunk in the morning is metabolised by your liver faster, and reaches your blood earlier, making you feel drunk faster, than if you had the same amount to drink in the early evening [3].

Blood alcohol levels are higher when drinking during the day. Adapted from Yap, 1993.

So how does the liver change its way that it breaks down alcohol? We think this is due to changing the concentration of an enzyme that metabolises alcohol, alcohol dehydrogenase. Experiments in rodents show that this enzyme is affected by the body clock [4]. It seems that our bodies have evolved to produce less of this enzyme later in the day, so we are able to tolerate alcohol better later in the day.

So bear in mind the next time you have a pint down the pub at lunchtime, you'll probably only need a half.


[1]    T. Danel and Y. Touitou, "Chronobiology of Alcohol : From Chronokinetics to Alcohol-related Alterations of the Circadian System," Chronobiology International, vol. 21, 2004, pp. 923-935.
[2]    R.H.L. Wilson, E.J. Newman, and H.W. Newman, "Diurnal variation in rate of alcohol metabolism," Journal of Applied Physiology, vol. 8, 1956, p. 556.
[3]    M. Yap, D.J. Mascord, G. a Starmer, and J.B. Whitfield, "Studies on the chronopharmacology of ethanol.," Alcohol and alcoholism, vol. 28, Jan. 1993, pp. 17-24.
[4]    F. Salsano, I.P. Maly, and D. Sasse, "The circadian rhythm of intra-acinar profiles of alcohol dehydrogenase activity in rat liver: a microquantitative study," The Histochemical Journal, vol. 22, Aug. 1990, pp. 395-400.