Although insomnia may not directly contribute to heart attack, but insomnia may affect blood pressure or inflammation – both risk factors for heart attack.
“Insomnia is a common sleep disorder that affects millions of people across the world. Hence, it is important that people are aware of this link between insomnia and heart attack, and consult to their physician if they have a sleep problem,” said lead researcher Dr. Lars Erik Laugsand, an internist from the Norwegian University of Science and Technology in Trondheim.
For the study, Laugsand and his team collected data on almost 53,000 men and women who participated in a national health survey in 1995-1997. They were asked to answer questions about their sleep habits. The researchers also identified about 2,400 people who had a first heart attack over the next 11 years.
The researchers found that people who have trouble sleeping almost every day had 45 percent increased risk of heart attack, compared with those without sleep problems.
In addition, people who have difficulty remaining asleep had a 30 percent increased risk of heart attack compared with those without the problems. Also people who didn’t feel refreshed after a night’s sleep had a 27 percent increased risk of heart attack, compared with those who felt fresh after a night sleep, the researchers added.
According to the researchers, 33 percent of general population has at least one insomnia symptom. Additionally, prior studies have found a smaller connection between insomnia and heart disease as well as heart attacks.
The researchers noted that there are two important limitations that need attention. First, they did not take into account for obstructive sleep apnea, a common disorder characterized by a pause of breathing during sleep. Second, the results may not apply to Africans or Americans because daylight time and sleep patterns are different than those in Norway.
“The finding only remains an association, and cause-and-effect has not been proven. Further studies are needed to confirm the findings and to reveal the possible mechanisms behind the association,” said Laugsand as reported by Healthday.
“These prior studies have yielded mixed results, and it still remains unknown whether better sleep leads to a healthier heart,” said Dr. Gregg Fonarow, professor of cardiology at the University of California, LA, and spokesman for the American Heart Association.
“One possible explanation for this finding is that all metabolic processes in the body is governed by what is called a circadian rhythms, which varies significantly between sleep-awake cycle,” said Dr. Edward A. Fisher, professor of Cardiovascular Medicine at NYU Langone Medical Center in NYC.
“It is known that animals with disrupted circadian rhythms are at risk of metabolic changes that, while in humans, are at increased risk of heart attack.”