Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Heart Disease Health Center

Font Size

Daylight Saving Time May Affect Heart

Study Shows Fewer Heart Attacks When Clocks Are Moved Back
WebMD Health News

Oct. 29, 2008 -- This weekend brings an end to daylight saving time, and if you're lucky enough to get an extra hour of sleep when you turn your clock back Saturday night, a new study suggests that it might save your life.

When researchers in Sweden examined the impact of daylight saving time on heart attack rates in that country, they discovered that people had slightly fewer heart attacks on the Monday after they set their clocks back in the fall and slightly more heart attacks in the days after they set their clocks ahead in the spring.

They presented their findings in a letter published in the Oct. 30 issue of The New England Journal of Medicine.

Study co-author Rickard Ljung, MD, PhD, says the results suggest that even small disturbances in sleep patterns may affect the heart.

"We know that Monday is the most dangerous day for heart attacks," he tells WebMD. "It has been thought that this is due to the stress associated with returning to work after the weekend, but our study suggests that disturbed sleep rhythms may be involved, and that the extra hour of sleep we get in the fall [after daylight saving time ends] may be protective."

Spring Forward, Fall Back

Ljung and colleague Imre Janszky, MD, PhD, of Stockholm's Karolinska Institute compared heart attack rates in Sweden between 1987 and 2006 in the week following daylight saving time to heart attack rates two weeks before and two weeks after the spring and fall events using a comprehensive national health registry.

They discovered a 5% increase in heart attacks in the first three workdays after clocks were set ahead for the beginning of daylight saving time in the spring and a similar decrease on the Monday after clocks were set back for the end of daylight saving time in the fall.

"That is not a big difference, but it was significant," Ljung says. It also may translate into sizeable numbers of individuals in absolute terms, given that 1.5 billion people are affected by daylight saving time shifts across the globe.

Today on WebMD

x-ray of human heart
A visual guide.
atrial fibrillation
Symptoms and causes.
heart rate graph
10 things to never do.
heart rate
Get the facts.
empty football helmet
red wine
eating blueberries
Simple Steps to Lower Cholesterol
Inside A Heart Attack
Omega 3 Sources
Salt Shockers
lowering blood pressure