One of the questions that keep individuals suffering with insomnia awake at night is whether there is a link between insomnia and heart disease.

A new study published, based on a large representative sample of the US population, helps to answer that.

The study, by Nicholas Vozoris, BSc, MHSc, MD, FRCPC, a respirologist at St. Michael’s Hospital, found that people with symptoms of insomnia did not have higher levels of cholesterol, one of the risk factors for cardiovascular disease, than people without insomnia.

The only exception was people with insomnia who took sleeping pills, who were 118% more likely to have high LDL cholesterol than people who took sleeping pills but did not have insomnia, a previously unknown association.

The study was published in the journal SLEEP.

Vozoris says many patients and healthcare providers may have wondered whether there was a link between insomnia and heart disease in part because of reports that another sleep disorder, sleep apnea, is linked with cardiovascular disease. There have been few research studies on the topic of insomnia and cholesterol, with conflicting results.

His study was based on the 2005-06 and 2007-08 National Health and Nutrition Examination Survey, a series of studies designed to assess the health and nutritional status of adults and children across the United States. The survey is unique in that it combines interview and laboratory data. Among all the people in the survey over age 20, 10.7% had elevated LDL cholesterol, 16.3% had high triglycerides, and 22.1% had low levels of HDL or healthy cholesterol. The chances of having abnormal cholesterol were not significantly different for the people who reported having symptoms of insomnia versus those who did not.

Vozoris says there have been two other studies, in Asia, looking at insomnia and cholesterol, with conflicting results, but that his was based on a much larger sample of people and included a wider range of variables, including markers of insomnia severity.

He says more research was needed into his new finding of higher LDL cholesterol among insomniacs taking sleeping pills compared to insomniacs who did not. For example, his data did not break down sleeping bills by class or brand of drugs.

“The observed link between sleeping pill use and elevated LDL cholesterol is particularly concerning given the dramatic rise in the use of sedative medicine in the general population in recent years,” he says in a release.

The finding may suggest that insomniacs who take sleeping pills simply have more severe insomnia, he says, and that more severe insomnia, rather than sleeping pill use, may be the reason for the high LDL cholesterol. But he said he found no evidence of higher LDL levels and other markers of insomnia severity, such as frequent insomnia, insomnia symptoms coupled with daytime fatigue, and insomnia symptoms coupled with short sleep time.