Sept. 3 (UPI) -- Getting too little or too much sleep may increase risk for heart attack as much as smoking, eating too much or not exercising, a new study says.
Sleeping fewer than six hours raises heart attack risk by 20 percent while getting more than nine hours raises the risk by 34 percent, according to research published Monday in Journal of the American College of Cardiology.
The good news is people with a genetic disposition to heart disease can lower the risk for heart attack by 18 percent when they sleep between six and nine hours a night, the study says.
"This provides some of the strongest proof yet that sleep duration is a key factor when it comes to heart health, and this holds true for everyone," Celine Vetter, a researcher at the University of Colorado at Boulder and study senior author, said in a news release.
For seven years, the researchers tracked medical data from the U.K. Biobank for 461,000 people between ages 40 and 69 who never had a heart attack.
The researchers then used Mendelian randomization to examine the effects of sleep on heart attack risk, independent of 30 other factors like body composition, mental health, physical activity and socioeconomic status. In all, 27 genetic variants were linked to shortened sleep time.
The researchers found the range for healthy sleep was between six to nine hours. Anyone who slept only five hours saw a 52 percent elevated risk for a heart attack compared to those who slept seven or eight hours. People who slept 10 hours had twice the risk.
Sleeping too little can affect the lining of the arteries and development of inflammatory cells, in addition to other poor life habits lack of sleep can influence. Conversely, sleeping too much can increase inflammation in the body, which can contribute to cardiovascular disease.
"This gives us even more confidence that there is a causal relationship here -- that it is sleep duration, not something else, influencing heart health," Vetter said.
"Just as working out and eating healthy can reduce your risk of heart disease, sleep can too," he added.