Clocks going back could be bad for our health – studies

Daylight saving time: Why are the clocks changed twice a year?

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October 30 this year marks the end of British Summer Time. As a result, the clocks will go back by one hour at 2am. Although for many people this will mean an extra hour in bed, it could wreak havoc on our sleeping patterns, and worse – lead to an increase in strokes and mental health issues.

The circadian rhythm refers to physical, mental and behavioural changes that abide by a 24 hour cycle. It is mainly influenced by sunlight and darkness and acts as our internal body clock.

However, it is believed that this can be thrown off when the clocks change – both backwards in October and forwards in March – leading to a whole host of issues.


One study, published in Sleep Medicine in 2016, showed how in the two days following both clock changes stroke rates are eight percent higher than usual.

As part of the research, the effect of daylight saving time transitions on ischemic stroke hospitalisations and in-hospital deaths was studied in Finland between 2004 and 2013.

It says: “Daylight savings time transitions appear to be associated with an increase in ischemic stroke hospitalisations during the first two days after transitions but not during the entire following week.

“Susceptibility to effects of DST transitions on the occurrence of ischemic stroke may be modulated by gender, age and malignant comorbidities.”

It also found that people with cancer were 25 percent more likely to have a stroke at that time than during other times of year.


It’s no surprise that the days getting suddenly shorter can affect mood. Research published in the Epidemiology journal proved a link between the clocks changing and depressive episodes.

“This study shows that the transition from summer time to standard time was associated with an increase in the incidence rate of unipolar depressive episodes,” it explains.

“Distress associated with the sudden advancement of sunset, marking the coming of a long period of short days, may explain this finding.”

Many people suffer from Seasonal Affective Disorder (SAD) during the winter, something that is exacerbated by the clocks changing. Common symptoms include a persistent low mood, a loss of pleasure or interest in normal everyday activities and feeling irritable.

Psychologist for the Cleveland Clinic, Susan Albers, added: “Seasonal affective disorder is often caused by changes in our circadian rhythm, that internal natural clock that runs our sleep, our mood and our appetite.

“When there is a shift in the season and our access to daylight, our bodies struggle to adjust to the new light and time frame.”


Building from the link between the clocks changing and depression, research has shown an increased rate in suicide at the same time. One paper, published in Sleep and Biological Rhythms, looked at Australian suicide data from 1971 to 2001. It found an increase in suicides both at the start and end of daylight savings.

“The results confirm that male suicide rates rise in the weeks following the commencement of daylight saving, compared to the weeks following the return to eastern standard time and for the rest of the year,” it says.

“After adjusting for the season, prior to 1986 suicide rates in the weeks following the end of daylight saving remained significantly increased compared to the rest of autumn.

“This study suggests that small changes in chronobiological rhythms are potentially destabilising in vulnerable individuals.”

Cardiovascular risks

Studies have shown there is actually a greater increase in the number of heart problems following the clocks going forward in the spring.

A study, found in the Journal of Clinical Medicine, says: “This meta-analysis showed a modest but significant increase in the risk of acute myocardial infarction (AMI) following daylight saving time (DST) transitions, that was particularly noticeable after the spring DST shift.

“Overall, these findings support the proposal of a DST transition discontinuation, although additional evidence is certainly needed to confirm the present results, identify high-risk subjects and quantify the relationship between DST transition and other severe diseases.”

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