Not getting enough sleep can double the chances of dying from heart disease or stroke, particularly in people with risk factors like diabetes, obesity, high blood pressure and cholesterol, U.S. researchers said Wednesday.

The findings in the Journal of the American Heart Association are based on 1,344 adults who were randomly selected for a sleep study in Pennsylvania.

The average age of participants was 49 and 42 percent of them were men.

The participants were recruited to undergo a series of health screenings and spent one night in a sleep laboratory.

Just over 39 percent were found to have at least three risk factors for heart disease and these factors, when clustered together, are known as metabolic syndrome.

Participants with the said risk factors had a body mass index (BMI) higher than 30 as well as elevated cholesterol, high blood pressure, elevated blood sugar and triglyceride levels.

Participants were followed for about 16 years and roughly 22 percent died during that period.

Those with metabolic syndrome who slept less than six hours in the lab were 2.1 times more likely to die of heart disease or stroke than those who did not have at least three risk factors for heart disease.

"Those who slept for shorter intervals with metabolic syndrome were also 1.99 times more likely to die of any cause compared to those who do not have metabolic syndrome," said the study.

High-risk participants who got more than six hours of sleep faced a 1.49 times higher risk of dying than healthier subjects.

Experts recommend that adults get at least seven to eight hours of sleep per night.

"If you have several heart disease risk factors, monitoring your sleep patterns and consulting a clinician if you have insufficient sleep are important if you want to lower your risk of death from heart disease or stroke," said lead author Julio Fernandez-Mendoza, an assistant professor at Penn State College of Medicine.

The study is described as the first of its kind, measuring the duration of sleep in a laboratory setting rather than relying on patient reports.

Researchers say it is also the first study to examine the impact of sleep duration on the risk of death in those with multiple heart disease risk factors.

However, since the study was observational in nature, it stops short of proving any definitive cause and effect relationship.

"Future clinical trials are needed to determine whether elongated sleep times, in combination with lowering blood pressure and glucose levels, would improve the prognosis of patients with the metabolic syndrome," said Fernandez-Mendoza.