That appears to be true even for people at genetic risk for such diseases.
These findings are important, for they underscore the connection between good sleep and cardiovascular health.
Unfortunately, poor sleep and unhealthy hearts are all too common in the United States. Cardiovascular diseases (diseases of the heart and blood vessels) are the leading cause of death for American men and women, claiming about 650,000 lives each year.
That’s one in every four deaths.
And Americans are significantly sleep deprived. Up to 70 million have a chronic sleep disorder severe enough to affect their daytime ability to function.
This study suggests that having healthy sleep patterns could lower the risk of developing heart disease, stroke and other cardiovascular diseases by as much as a third.
Plenty of previous research has examined the relationship between sleep and cardiovascular disease. But most of those studies focused on a single sleep-related problem, such as not getting enough sleep or snoring.
The authors of new study — a team led by Dr. Lu Qi, director of the Tulane University Obesity Research Center — decided to take a broader look at the topic. First, they created a “healthy sleep score” that combined five separate factors:
- being a “morning” rather than an “evening” person;
- sleeping 7 to 8 hours most nights (the recommended amount for adults);
- never or rarely experiencing insomnia (difficulty falling asleep or waking in the night);
- not snoring; and
- not being sleepy during the daytime.
The researchers then applied that sleep score (one point for each factor) to 385,292 British adults who were participating in UK Biobank, an ongoing study aimed at finding better ways to prevent, diagnose and treat a wide range of serious and life-threatening illnesses, including cardiovascular disease. The participants were aged 37 to 73 when they were recruited into the study, and none had cardiovascular disease at that time.
At the start of the study, the participants filled out detailed questionnaires about their lifestyle behaviors, including their sleep patterns. They also provided genetic samples.
About 22 percent of the participants had sleep scores of 5 (the healthiest), while about 2 percent has scores of 0 or 1 (the least healthiest).
Qi and his colleagues followed the participants for an average of 8.5 years. During that period, 7,280 of them developed heart disease or stroke.
“We wanted to test whether the relation between sleep scores and cardiovascular outcomes was different according to the genetic risk. This is the first time this has been done,” says Qi in a released statement.
“We also wanted to estimate the proportion of cardiovascular problems that would not have occurred if all participants had a healthy sleep pattern, if we assume there is a causal relationship,” he adds.
After adjusting the data for a number of factors that can affect both sleep quality and cardiovascular risk, such as age, body mass index, smoking and physical activity levels, the researchers found a link between the participants’ sleep scores at the start of the study and their likelihood of developing cardiovascular disease by its end.
Specifically, they found that compared to those with an unhealthy sleep score of 0-1, those with a healthy score of 5 had a 35 percent lower risk of cardiovascular disease, including a 34 percent reduced risk of heart disease and stroke.
This meant there were almost seven fewer cases of cardiovascular disease per 1,000 people per year among those with a sleep score of 5 than among those with a score of 0-1.
Yet, it wasn’t only the people with the highest sleep scores who saw their risk fall. Each point above an unhealthy score appeared to drop the risk of heart attacks or stroke by about 8 percent.
The researchers then looked to see if genetic risk for cardiovascular disease affected the findings. It did. People with a high genetic risk were less likely to develop heart disease and stroke if they had healthy sleep patterns.
Limitations and implications
This study is observational, which means it can’t prove cause and effect. Indeed, as the study’s authors point out, although none of the participants had signs of cardiovascular disease at the start of the study, those with poor sleep patterns may have had another undetected health problem that contributed to their risk of cardiovascular disease.
Another limitation of the study was that the participants reported their own sleep patterns. Such self-reports can be unreliable. In addition, most of the UK Biobank participants are of European descent, so the study’s findings may not be applicable to broader populations.
Despite these limitations, Qi believes the study’s findings suggest, at a minimum, “that it is essential to consider overall sleep behaviors when considering a person’s risk of heart disease or stroke.”
“If the link between sleep and cardiovascular disease proves to be causal, then more than a tenth of all heart disease and strokes would not have occurred if all the participants had a healthy sleep score of five,” he points out.