Timing for health

Timing for health

The health impacts of circadian rhythms

Sheila Moorcroft, Research Director

Last spotted
6 May 2011

Timing – such as the season of birth or conception or the time of day of a heart attack – may have more impact on our health than previously thought – increasing risks and vulnerabilities. Might we soon see greater monitoring of, advice about and tests for timing related health issues?
What is changing?
New research projects indicate a variety of potential links between season of birth/ conception and health in later life. Research by the Wellcome Trust indicated an increase in the incidence of anorexia associated with births in the spring. Survival rates of babies born between April and October is lower than those born the rest of the year according to Spanish research. A major review in the US of 30 million births indicated a 3% increase in birth defects during April- June, relative to the rest of the year. Research in Finland highlighted possible links to increased allergies among those whose mothers were 11 weeks pregnant during April and May. Research on mice indicates a potential link between season and mental health and activity levels in later life: those born in winter have more problems.

Research into heart attacks indicates that those which occur earlier in the day – between 6am and noon, tend to be more severe, damaging more of the heart. In addition, more occur during that time. Monday meanwhile is the more common day for heart attacks among those who work.

Why is this important?
While not conclusive, these new areas of research on the timing of births indicate sufficient links to merit further investigation. The timing related patterns may indicate underlying or wider issues such as higher levels of pollens or chemicals affecting mother and foetus; reduced exposure to and absorption of Vitamin D and other dietary issues; levels of smog and pollution remaining in the atmosphere; changes in diet; length of exposure to daylight; variations in body functions over time. For example, with regard to heart attacks – our bodies’ natural circadian rhythms influence the level of critical, and damaging, enzymes released in morning heart attacks.

As our ability to monitor and measure bodily systems and functions in real time improves and becomes far less cumbersome, could full-time monitoring of pregnant women might become part of ante-natal care – not only to protect mothers and babies, but also to build an adequate research base? Just as we have seen the development of easy to use pregnancy tests or predictors of ovulation, could we see the development of test kits – and advice – for timing related foetal / long term health issues? Will post-natal advice and support need to change to try to reduce the impacts of such seasonal issues? Will we see the development better daylight substitute lighting that can truly replicate the wider beneficial aspects of daylight? Will the pattern of births over the year become distorted increasing the peaks and troughs of demand for maternity services? Could real-time monitoring of blood enzyme patterns etc among those at risk of heart attacks reduce the severity or occurrence of heart attacks?

The health impacts of circadian rhythms – the amount and type of light we are exposed to and its impact on physical and mental health – have been researched and discussed for many years. Jetlag, Seasonal Affective Disorder, long-term effects of shift work are among the most widely discussed impacts. Seasonal and other timing related issues may soon join them.


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