Every year on the last Sunday in October at 2am, the clocks in Britain go back, signaling the start of shorter days.
This year, the clocks will go back an hour at 2am on Sunday, October 27, giving us an extra hour in bed as we prepare for the colder winter months.
While most of us welcome an extra hour of sleep, the system of changing the clock twice a year can be controversial due to health and behavioral issues related to changing sleep patterns and adapting to dark evenings. And some studies have shown that it disrupts the body's natural sleep cycles, which can affect both physical and mental health.
So what is the impact of turning back the clock on our health?
How does changing the clock affect physical health?
The human brain has a biological clock, also called a circadian rhythm, which runs on a 24-hour cycle.
Whether gaining an extra hour or losing an hour of sleep, this disrupts the sleep cycle and can make it difficult for some people to adjust back to a normal schedule. Disturbed sleep may also lead to a higher risk of cardiovascular disease.
A 2019 study by researchers at Harvard Medical School and Massachusetts General Hospital examined the impact of sleep deprivation on heart disease in mice. It was found that mice whose sleep cycles were disrupted developed larger arterial plaques after 16 weeks compared to mice with normal sleep patterns.
The sleep-deprived mice also had twice as many white blood cells in their circulation, and lower levels of hypocretin, a hormone that plays a key role in regulating sleep and wakefulness.
“This appears to be the most direct demonstration yet of the molecular connections linking blood and cardiovascular risk factors with sleep health,” said Dr. Michael Twery, director of the National Center on Sleep Disorders Research at the National Heart, Lunch and Blood Institute in the USA
The loss of an hour of sleep during the spring time change has been linked to an increase in heart attacks and strokes. In the US, hospitals report a 24 percent spike in heart attack visits every year on the Monday after the clocks go forward.
Research has also shown an increase in car accidents when the clocks go back in the colder months, as drivers adjust to the time change.
According to data from Zurich Insurance, drivers are more likely to have an accident in November between 4 p.m. and 7 p.m. because the evenings get dark earlier. After the clocks were changed, the company noticed a 10 to 15 percent increase in accidents during that period compared to the rest of the day.
How does changing the clock affect mental health?
When the clocks go back in the fall, we get an extra hour of daylight in the morning. However, this only lasts for a few weeks before the days get shorter and the sunrise gets later and later.
On the shortest day of the year, December 21 or 22, Britain enjoys less than eight hours of sunlight.
The longer hours of darkness can result in low mood and depression in some people, as well as fatigue, muscle pain and weakened bones due to a vitamin D deficiency from sunlight exposure.
Some people also experience seasonal affective disorder (SAD) as a result of the shorter days. According to the NHS, SAD symptoms include persistent low mood, loss of interest in normal daily activities, irritability, feelings of despair or guilt, and sleeping longer than usual.
The health agency says the lack of sunlight can cause a part of the brain called the hypothalamus to not work properly, which can affect the production of melatonin (a sleep hormone) and serotonin (a mood hormone), as well as the body's circadian rhythm . .
