Suffering from insomnia may increase people's risk of heart attack or stroke, scientists have said. Women appear to be slightly more vulnerable, suggesting that it may be important to pay careful attention to their sleep health.

Symptoms of insomnia have sometimes been linked to a higher risk of cardio-cerebral events in past studies, but findings on the subject have remained inconsistent.

To settle the debate, researchers have conducted a large meta-analysis, now published in the European Journal of Preventive Cardiology, going through published scientific literature dealing with insomnia and cardio-cerebral health.

The scientists selected 15 prospective cohort studies from the scientific data base Cochrane, PubMed and Web of science. Taking together, all these research had followed a total of 160 867 participants.

During a median follow-up of three to 29.6 years, 11 702 heart attacks and strokes had occurred.

Better follow-up of insomniac patients

The team found that there were significant associations between three symptoms of insomnia – difficulty initiating sleep, difficulty maintaining sleep, and non-restorative sleep – and the risk of heart disease and stroke. However, there was no association between early-morning awakening and adverse health events.

"We found that difficulty initiating sleep, difficulty maintaining sleep, or non-restorative sleep were associated with 27%, 11%, and 18% higher risks of cardiovascular and stroke events, respectively", first author Qiao He from China Medical University, said.

The meta-analysis makes a compelling cases that insomnia symptoms increase the risk of cardio-cerebral events. Although these are only correlations, monitoring the cardio-cerebral health of insomniac patients may be important.

More research will be needed, because the reasons behind the association are still unclear. "The underlying mechanisms for these links are not completely understood," He added. "Previous studies have shown that insomnia may change metabolism and endocrine function, increase sympathetic activation, raise blood pressure, and elevate levels of pro-inflammatory and inflammatory cytokines – all of which are risk factors for cardiovascular disease and stroke."

The researchers also found that insomniac women were slightly more at risk of heart attack and stroke than insomniac men, although this was not statistically significant. While they are unable to conclude that insomnia is much more dangerous for women, the results may influence clinicians to conduct an even closer follow-up of women with sleep problems.

"We do know that women are more prone to insomnia because of differences in genetics, sex hormones, stress, and reaction to stress. It may therefore be prudent to pay more attention to women's sleep health", He concluded.