Although research suggests that people who find it harder to fall asleep may have slower heart-rate recovery times and that short sleep duration and poor sleep quality can increase the risk of heart disease, limited data exists on the joint effects of sleep duration and sleep quality. This prompted researchers to conduct a prospective cohort study to investigate the effect of sleep on the development of heart disease. The study involved more than 60,000 adults and was published in the Journal of Clinical Sleep Medicine in 2018.
Researchers analyzed data collected on 60,586 adults over the age of 40 (the average age of participants was 50). Participants received a series of medical exams and filled out a self-administered questionnaire at the start of the study. Participants who received a new diagnosis of coronary heart disease on a future visit were defined as having a new event of coronary heart disease.
Participants were asked how many hours they usually slept each day. They were also asked to evaluate their sleep over the previous month based upon whether they used sleeping pills or other medications to sleep, how well they fell asleep, whether they woke during the night, and how well they slept.
Over the course of the study, just under five percent of participants reported a coronary heart disease diagnosis. No significant difference was found between genders, but incidence rates were found to increase by age until participants reached age 75 (incidence rates decreased at that point).
Coronary heart disease and sleep
The study found that higher sleep quality scores significantly decreased the risk of coronary heart disease. In fact, every five-unit increase in sleep quality score was associated with a nine-percent decrease in coronary heart disease risk.
Researchers also found that a significantly higher risk of coronary heart disease was observed in those who found it difficult to fall asleep and those who used sleeping pills or other drugs to help them sleep. A sleep duration of under six hours per day was also found to significantly increase coronary heart disease risk (long sleep duration did not reach statistical significance).
The role of sleep duration and sleep quality
This was the first cohort study to take both sleep duration and sleep quality into consideration when investigating the association between sleep and incidence rates of coronary heart disease. It concluded that both poor sleep quality and short sleep duration were independently associated with coronary heart disease risk in adults over 40 years of age.
Why does sleep influence heart health?
There are several theories. As the authors of this study pointed out, one possible explanation is that poor sleep can influence levels of leptin and ghrelin — hormones that regulate energy expenditure and hunger. This, in turn, may increase obesity risk, which can have a negative effect on heart health.
Another theory is that sleep disruption can lead to higher levels of cortisol (a stress hormone) — and this can be hazardous to heart health over time. Short sleep durations are also associated with inflammation, which can trigger the body’s stress response. This can lead to increased blood pressure and an increased risk of heart disease.
What to do next
This study highlighted the importance of both sleep duration and sleep quality when it comes to our overall health. It’s important not to simply target “more sleep” since sleep quality is just as vital as sleep duration.
Cognitive behavioral therapy for insomnia (CBT-I) can help improve sleep quality and sleep duration without the use of sleeping pills (my free insomnia sleep training course uses cognitive and behavioral techniques to help insomnia sufferers improve their sleep over a two-week period). If you have been diagnosed with insomnia or are having sleep issues, ask your doctor if CBT-I is available in your area.
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Martin is the creator of Insomnia Land’s free insomnia sleep training. His online course uses CBT techniques to teach participants how to sleep better without relying on sleeping pills. More than 5,000 insomniacs have completed his course and 97 percent of graduates say they would recommend it to a friend.