Seven really is the lucky number - at least when it comes to sleep.
Often sleeping less than 7 hours a day is connected to an increased risk for heart disease, say researchers at West Virginia University School of Medicine.
But it does not mean that more sleep is better: The researchers also found that regularly sleeping more than 7 hours a day is also associated with increased heart disease risk.
They published their findings in the August 1, 2010 issue of the journal "Sleep."
Analyzing data from more than 30,000 adults, all of whom were healthy at the start of the study, they found that short and long sleep duration were associated with increased heart disease risk even when they controlled for age, sex, race, ethnicity, smoking, alcohol intake, and other risk factors.
Adults who slept less than 5 hours a day (including naps) were more than twice as likely to develop heart disease. Those who slept 9 hours or more each day also had an elevated risk of cardiovascular disease--they were 1.5 times more susceptible, according to the report. It was found that an "elevated but less dramatic risk" of cardiovascular health issues in those who slept for either 6 or 8 hours each day, according to the press release.