We don’t often make the connection between our health and our relationship to the sun but a good daily dose of daylight has a major impact on our wellbeing.
Humans and all other living organisms on the planet evolved in an environment which was VERY bright during the day and VERY dark during the night.
We are connected to the sun in a profoundly physiological way and this internal clockwork or ‘circadian rhythm’ controls hormones, mood, appetite and signals to different parts of the body to function differently depending on the time of day.
For instance, resting heart rate changes during the day or night, regardless of activity. If you are lying on the flat of your back you will have a more increased heart rate during the day than if you are in the same pose doing nothing during the night. Same with blood pressure. Digestion also works differently during the day vs the night and is generally active during the day and slows at night which is why curry chips from Lennox’s at 2am may not be a great idea!
There are 20,000 specialised cells in our brains that are stimulated by light, these cells are our ‘master clock’. They influence when we are wakeful or sleepy and other important biological functions throughout the day. However, since the advent of electricity and more sedentary indoor lifestyles, we are living our lives almost like we are underground.
If you measure light on a sunny day and take a Lux meter outside - you’ll probably register 10,000 lux. Bring the meter inside and you’ll only reach about 300-400 lux. We spend 80% of our time indoors and this has a major impact on our circadian rhythms because our master clocks don’t get the light stimulus they need and give out strong signals to the rest of the body.
Last year I interviewed Dr Annie Curtis, a researcher at the Royal College of Surgeons Ireland, and she really emphasised the importance of light for our health and immune systems.
Her research studies the effects of the circadian rhythm on immunological conditions like Rheumatoid Arthritis which follow a very predictable pattern over the course of the day.
She said there are 20,000 cells in the hypothalamus of our brain that are stimulated by light, these cells are our ‘Master clock’. They influence when we are wakeful or sleepy and other important biological functions throughout the day.
There are lots of night time medical conditions e.g. nocturnal asthma and nocturnal epilepsy which, for some reason, only occur at night time and give an inkling of the complexity of what goes on in the body and how the circadian clocks effect things.
Seasonal Affective Disorder (SAD) is a condition which is light dependent. People experience low mood and energy during the darker months of the years and Ireland has a pretty high rate because our weather can be so oppressive during the winter that getting outside is difficult.
Rates of SAD among populations increases as you go up (or down) the latitudes. Very little SAD in Africa and countries on the Equator, plenty of it in Nordic countries where days are very short in winter. The most effective treatment for SAD comes from a light lamp that emits 10,000 lux.
Wouldn’t it be wonderful if more conditions could simply be treated by light!
We tend to think of circadian rhythms in terms of a 24 hour clock but there is also a seasonal aspect to it. Some of the reasons that Winter is cold and flu season is not necessarily because everyone is cold or there are more bugs but possibly because our immune systems are suppressed during the winter months due to lack of light.
So light, or lack of it, is not some innocuous health factor. It is an important part of our environment just like good air or water quality.
Some companies, realising the importance of light for regulating our biological, physiological and emotional wellbeing, have started considering lighting design in office environments and are increasing the lux levels in workplaces. The logic being, happy workers equal better productivity, equals better profits. For the price of a few extra bulbs!
All this points to the need to abandon daylight savings time (DST). The reasons for DST is outdated and the science to support ending it is very strong.
We are willingly giving ourselves jetlag twice a year to the detriment of our health.
One study showed a 25% increase in the number of heart attacks in the US following the spring forward of daylight saving time, the theory being an hour less sleep has a negative effect on health.
Another study showed there are more car accidents the Monday after switching DST in the Spring – possibly caused by tired drivers.
Last year the European parliament voted to scrap daylight savings time from 2021 but ironing out the nitty gritty is complicated. Ireland and the UK need to be in the same timezone so we don’t have the bizarre scenario of Belfast and Dublin being an hour apart. For health reasons we should stick with ‘winter time’ all year to maximise our exposure to light during the winter months. It means no more ‘grand stretches’ until 10pm in the summer time. But I think we’ll cope.