SUNDAY, March 25 (HealthDay News) -- When it comes to what's best for their hearts, people walk a fine line between getting too much and too little sleep, a new study suggests.

Adults who get fewer than six hours or more than eight hours of sleep a night are at greater risk for a variety of heart conditions, according to research led by Dr. Rohit Arora, chairman of cardiology at the Chicago Medical School.

Sleeping too little puts people at significantly higher risk of stroke, heart attack and congestive heart failure, the researchers found. On the other hand, people who sleep too much have a higher prevalence of chest pain (angina) and coronary artery disease, a narrowing of the blood vessels that supply the heart with blood and oxygen.

The findings are scheduled for presentation Sunday at the American College of Cardiology annual meeting in Chicago.

The researchers analyzed data from more than 3,000 patients over age 45 who participated in the U.S. National Health and Nutrition Examination Survey, making theirs the first nationally representative sample to show the association between sleep duration and heart health.

The study showed that people who got too little sleep were twice as likely to have a stroke or heart attack and 1.6 times more likely to have congestive heart failure. People who slept more than eight hours a night were twice as likely to have angina and 1.1 times more likely to have coronary artery disease.

The findings remained significant even after the researchers accounted for heart risk factors such as age, blood cholesterol levels, smoking and obesity, as well as for sleep apnea and other sleep problems.

Previous studies have shown that insufficient sleep is linked to a hyperactive nervous system, glucose intolerance, diabetes, inflammation and a rise in stress hormones, blood pressure and resting heart rate, the researchers noted.

The reasons too much sleep can lead to heart problems are unclear, however, and further research will be needed.

For now, Arora said, health-care providers need to talk about sleep with their patients.

"Clinicians need to start asking patients about sleep, especially those who are already at greater risk of heart disease," he said. "It's really a simple thing to assess as part of a physical exam; it doesn't cost anything and it may help patients to adopt better sleep habits."

Although the new study uncovered an association between sleep issues and heart trouble, it did not prove a cause-and-effect relationship.

Research presented at medical meetings should be viewed as preliminary until it is published in a peer-reviewed medical journal.

More information

The National Sleep Foundation has more on getting a good night's sleep.