Winter-summer hour changes have impact on health

Putting clocks forward has ‘enormous impact’ on health

Seasonal changes can reduce immunity

By Judith Duffy, Health Correspondent
http://www.sundayherald.com/news/heraldnew...t_on_health.php


IT'S A convention which allows us to enjoy long summer evenings, but switching to daylight savings time could also be responsible for drastically disrupting the body's internal clock.

According to researchers, the one-hour time jump that takes place in the spring - when clocks are put forward one hour- can result in people's natural circadian rhythms being disturbed for nearly a fifth of the year.

And they argued this could be having an "enormous" impact on health by interfering with the body's "seasonal" defences to viruses.

A study was carried out by tracking the sleep patterns of 65,000 people in Europe and noting their "mid-sleep" point, which is half way between the point of falling asleep and waking up on days off.

Lead researcher Till Roenneberg, professor of chronobiology at Ludwig-Maximilians University, Munich, said the body adjusts to dawn when coming out of the winter months, but when daylight savings time (DST) is introduced, this process"abruptly stops".

"If we are getting up in winter, the sun rises after we have got up," he explained. "Then we are progressing into spring and for some days we are getting up with the sun - then in the following weeks after that, the sun rises before we get up.

"With the DST change in spring, we suddenly have to get up again before the sun rises - this little one-hour time change throws our annual trajectory back by four weeks."

He added: "In autumn it is even worse, it is thrown back by six weeks, so on the seasonal scale the one little hour perturbs the system by 10 weeks, a significant 20% of the entire year."

Roenneberg pointed out the ability of humans in the Western world to adjust to the changing seasons had already been disrupted by modern indoor living which reduces exposure to fluctuations in temperatures and light, but argued DST was "messing about with the system even more".

"Over the course of seasons, we are exposed to different enemies' such as bacteria and viruses, which our immune system should be able to fight against," he said. "Biological internal timing systems have evolved to accommodate and anticipate environmental changes, so they can react appropriately and proactively.

"If we are perturbing these systems, we could potentially prevent our seasonal adaptation to be really effective. In general, the consequences may be minor, but if you add them up they could lead to enormous health costs."

Roenneberg said further research was now planned to examine the differences between people living in countries without DST compared to those which have it.

"We should take this very seriously and investigate the potential consequences of DST," he added.

The idea behind DST is that moving the clocks forward in the summer allows us to take better advantage of daylight hours, but it has provoked continued controversy since being introduced in the early part of the 20th century.

Germany first used the idea in the spring of 1916, to conserve energy by replacing artificial light with daylight in the evenings during the war, and Britain and its allies then followed suit.

However some critics argue that there is a lack of evidence to back up the continuation of the practice. One study published last year estimated turning the clocks back each winter causes domestic consumers to use an extra 5% of electricity and a related surge in greenhouse gas emissions.

The Royal Society for the Prevention of Accidents (Rospa) is among those who have called for changes, which it argues would reduce road accidents in the winter. But it wants a single/double summertime system introduced, where the clocks would not revert to GMT in autumn and then move a further hour forward every spring. However, this has been opposed particularly in Scotland, as it would result in dawn occurring as late as after 10am in the far north.

Kevin Clinton, Rospa head of safety, said: "Ideally we would like the government to agree to a three-year trial to prove the road safety arguments."