Turning Clocks Back May Help Your Heart

Swedish Study Finds Cardiac Arrests Dip Days After Daylight Savings Switch

(CBS/ AP)  Turning your clock back on Sunday may be good for your heart.

Swedish researchers looked at 20 years of records and discovered that the number of heart attacks dipped on the Monday after clocks were set back an hour, possibly because people got an extra hour of sleep.

But moving clocks forward in the spring appeared to have the opposite effect. There were more heart attacks during the week after the start of daylight saving time, particularly on the first three days of the week.

"Sleep - through a variety of mechanisms - affects our cardiovascular health," said Dr. Lori Mosca, director of preventive cardiology at New York-Presbyterian Hospital, who was not involved in the research. The findings show that "sleep not only impacts how we feel, but it may also affect whether we develop heart disease or not."

The study was described in a letter published in Thursday's New England Journal of Medicine by Dr. Imre Janszky of the Karolinska Institute and Dr. Rickard Ljung of Sweden's National Board of Health and Welfare.

Janszky said he came up with the idea for the study after last spring's time change, when he was having problems adjusting.

"I was on the bus, quite sleepy, and I thought of this," said Janszky, who has done other research on sleep and health.

They took advantage of Sweden's comprehensive registry of heart attacks to see if the disruptions to sleep and the body's internal clock caused by a time change had any effect on heart attacks from 1987 to 2006. They compared the number of heart attacks on each of the seven days after the time shift with the corresponding day two weeks earlier and two weeks later.

Overall, in the week after "spring forward," there was a 5 percent increase in heart attacks, with a 6 percent bump on Monday and Wednesday and a 10 percent increase on Tuesday. In the week after "fall back," the number of heart attacks was about the same, except on Monday, which had a 5 percent decrease.

"The finding that the possibility of additional sleep seems to be protective on the first workday after the autumn shift is intriguing," the authors wrote.

CBS Early Show co-anchor Harry Smith quipped that the dip in heart attacks stems from the lack of anxiety associated with turning the clock back an hour, as opposed to in the spring, when dialing time ahead could create stress.

Doctors have long known that Monday in general is the worst day for heart attacks, and they usually blame the stress of a new work week and increased activity. The Swedish researchers said their findings suggest that the minor loss of sleep that occurs at the end of ordinary weekends - with people going to bed later on Sunday and getting up early on Monday - might also be a contributing factor.

Last year, a study by American researchers found there were more pedestrian deaths during the evening rush hour in November than October as drivers and pedestrians adjust to the earlier darkness. They said the risk for pedestrians drops in the spring when clocks are set back and daylight comes earlier.

Daylight saving time in the United States ends this year at 2 a.m. Sunday. All states except Arizona and Hawaii will make the switch. Sweden and the rest of Europe turned back their clocks last weekend. More than 1.5 billion people worldwide live in countries that use daylight saving time, the researchers said.

Sweden has a moderate rate of heart attacks and is at a high latitude, but Janszky said he would expect roughly the same results elsewhere.

Sleep can affect the heart through changes in blood pressure, inflammation, blood clotting, blood sugar, cholesterol and blood vessels, Mosca said. She suggested that anxiety from changes in routine may also be a factor, in addition to loss of sleep.

Dr. Ronald Chervin, director of the University of Michigan's Sleep Disorders Center, said this is a "sleep-deprived society," and he advises taking advantage of Sunday's time change and getting an extra hour of sleep.

In the spring, he suggests gradually adjusting to the one-hour loss by going to bed and getting up 15 minutes earlier for a few days before the time change.

"We spend a third of our lives sleeping and people forget how much effect it has on overall health," he said.

Incidence Ratios of Heart Attacks on the First 7 Days after the Spring and Autumn Clock Shifts for Daylight Saving Time (1987-2006).

(New England Journal of Medicine)

[mtminds]

Why even use standard time? The US should stick to Daylight Savings Time. Why you ask? Because it will save energy. Less light bulbs being turned on at 5 o''clock, when a family is still at peak activity. Who needs the sun at 6 o''clock in the morning?

[erasmus81]

I''''m one of many who finds it extremely difficult and unsettling to adjust to losing an hour of sleep, versus gaining an hour of sleep. And it takes months for my body to adjust.
Posted by Credibility2 at 12:20 PM : Oct 31, 2008


I don''t see what the big freakin deal is. Quit whining and go to bed earlier.

[ybotheratall]

Parents don''t get any extra sleep you morons. Our stress just starts an hour earlier. The idiots who came up with DST should be drawn and quartered. Stupidest thing I''ve ever heard of. We should stay on regular time ALL year round and this ridiculous forward and back idiocy needs to END.

[incog-nito]

The solution is clear, then: Give people an hour more for sleeping and an hour less for working. More sleep, less stress. This will reduce heart attacks big time.

Somehow I don''t see this happening anytime soon. So much for this study.

[luvcomments]

I never turn my clocks back (or forward). I keep them on summer time. I simply re-set the alarm clock. I wonder if this will give me a heart attack?

[credibility2]

This finding was enlightening. I''m one of many who finds it extremely difficult and unsettling to adjust to losing an hour of sleep, versus gaining an hour of sleep. And it takes months for my body to adjust. What this study and finding reveals that there is a toll to many on the loss of one hour of sleep forced upon them by the time change. Maybe this should be abolished since it''s original purpose isn''t that valid anymore, which I believe was to aid the farmer in their planting and harvest times.