Heart attack risk higher in those who sleep too little or too much
The right amount of sleep is protective of heart health. This was the conclusion of new research that found sleep duration can influence a person's risk of heart attack, regardless of other heart risk factors, including genetic ones.
In a recent Journal of the American College of Cardiology paper, scientists from the United States and the United Kingdom describe how they analyzed sleep habits and medical records of 461,347 people aged 40–69 years living in the U.K.
The data, which came from the UK Biobank, included self-reports of how many hours participants habitually slept per night and health records covering 7 years. It also included results of tests for risk genes.
The analysis revealed that those who slept less than 6 hours per night had a 20% higher risk of a first heart attack in comparison to those who slept 6–9 hours. Those who slept more than 9 hours had a 34% higher risk.
The researchers also found that keeping sleep duration to 6–9 hours per night can reduce the risk of a first heart attack by 18% in those people with a "high genetic liability" for developing heart disease.
"This [study]," says senior study author Celine Vetter, Ph.D., an assistant professor of integrative physiology at the University of Colorado at Boulder, "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."
Sleep duration is an independent risk factor
Studies have been finding links between sleep habits and heart health for some time now. However, most of those findings have come from observational studies: these studies that can only confirm links but cannot establish the direction of cause and effect.
Because many factors affect both sleep and heart health, it is not easy to determine whether poor sleep makes for poor heart health or poor heart health leads to poor sleep.
Vetter and her colleagues sought to meet this challenge by using data from a vast number of individuals, combining it with genetic research, and ruling out dozens of potential influencing factors.
Altogether, they adjusted the results to remove the potential effect of 30 factors that can influence both heart health and sleep. These factors include physical activity, mental health, income, education, smoking, and body composition.
The researchers' results showed that sleep duration was an independent risk factor for heart attack.
The researchers found that the risk of heart attack increased the further that people's habitual night sleep diverged from 6–9 hours.
Individuals who slept 5 hours each night, for example, had a 52% higher risk of a first heart attack than those who slept 7–8 hours. Individuals who slept 10 hours per night had double the risk.
