March 31 (UPI) -- A new study has found a link between insomnia and an increased risk of a person having a heart attack or stroke.
"Sleep is important for biological recovery and takes around a third of our lifetime, but in modern society more and more people complain of insomnia," Qiao He, a researcher at China Medical University, said in a press release. "For example, it is reported that approximately one-third of the general population in Germany has suffered from insomnia symptoms. Researchers have found associations between insomnia and poor health outcomes. But the links between insomnia and heart disease or stroke has been inconsistent."
Researchers analyzed 15 cohort studies of 160,867 people who were followed for an average of three to 29.6 years, examining the relationship between insomnia and incidence of or death from cardiovascular disease.
Cardiovascular disease was defined as acute myocardial infarction, coronary heart disease, heart failure, stroke or a combination of events, and insomnia was defined as difficulty falling asleep, staying asleep, early-morning awakening and non-restorative sleep.
The study found significant associations between difficulty falling asleep, difficulty staying asleep and non-restorative sleep and an increased risk for heart disease and stroke.
"We found that difficulty initiating sleep, difficulty maintaining sleep, or non-restorative sleep were associated with 27 percent, 11 percent and 18 percent higher risks of cardiovascular and stroke events, respectively," He said. "The underlying mechanisms for these links are not completely understood. Previous studies have shown that insomnia may change metabolism and endocrine function, increase sympathetic activation, raise blood pressure, and elevate levels of proinflammatory and inflammatory cytokines -- all of which are risk factors for cardiovascular disease and stroke."
The study showed women with insomnia symptoms were at a slightly higher risk than men for developing cardiovascular disease or stroke. He said, however, that the difference was not statistically significant.
"We cannot conclude that insomnia is more dangerous for women, given the limitations of meta-analysis and the lack of a statistically significant difference between sexes," He said. "However, 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."
The study was published in the European Journal of Preventive Cardiology.