The effect of the transition to summer time on health

By Associated Press

The good news: You’ll get a great extra hour of sleep. The Bad: Late nights will be pitch black in the US for the next few months

Daylight Savings Time ends at 2 a.m. local time next Sunday, November 3, which means you should turn your clocks back an hour before you go to bed. Standard Time will continue until March 9, when we jump forward again with a return to summer time.

This spring time change can be more difficult on your body. Darker mornings and lighter evenings can throw off your internal body clock, making it harder for you to fall asleep on time for weeks or longer. Studies have even found a spike in heart attacks and strokes immediately after the March time change.

“Backing off” should be easier. But it can still take some time to adjust to your sleeping habits, not to mention the downsides of leaving work in the dark or trying to exercise while there’s still plenty of light. Some people with seasonal affective disorder, a type of depression typically associated with shorter days and less sunlight in the fall and winter, can also have a hard time.

Some health groups, including the American Medical Association and the American Academy of Sleep Medicine, have said it’s time to ditch the time switches and that standard time is better aligned with the sun and human biology.

Most countries do not observe summer time. For those that do—mostly in Europe and North America—the clocks change date varies.

Two states – Arizona and Hawaii – do not change and remain on standard time.

Here’s what you need to know about the twice-yearly ritual.

How the body reacts to light

The brain has a master clock that is set by exposure to sunlight and darkness. This circadian rhythm is a roughly 24-hour cycle that determines when we become sleepy and when we are more alert. Patterns change with age, one reason early risers turn into hard-to-wake teenagers.

The morning light resets the rhythm. By evening, the level of the hormone melatonin begins to rise sharply, causing drowsiness. Too much light in the evening—that extra hour after daylight saving time—delays that surge and throws the cycle out of sync.

And this circadian clock affects not only sleep, but also heart rate, blood pressure, stress hormones, and metabolism.