Individuals looking to lower their risk for cardiovascular problems may want to focus on sleeping just the right amount. A new study published in the journal Sleep has found that sleeping for less than five hours per day or more than seven hours per day increases the risk of chest pain, heart attack or stroke.

Researchers at West Virginia University analyzed data from more than 30,000 healthy adults for the findings.

They found that both short and long sleep duration was associated with increased heart disease risk even when they controlled for age, sex, race, ethnicity, smoking, alcohol intake and other risk factors.

Researchers say that sleeping less than five hours each day, including naps, more than doubles an individual’s heart risks. At the same time, sleeping for more than nine hours each increases the risk of cardiovascular disease by one and a half times.

Scientists say that the duration of sleep affects both endocrine and metabolic functions. Lack of sleep can lead to high blood pressure, impaired glucose tolerance, and reduced insulin sensitivity, which can all lead to hardening of the arteries.