Poor sleep linked to earlier onset of cardiovascular disease

Along with regular exercise and a balanced diet, sleep is an essential component of a healthy lifestyle. Although the World Health Organization recognizes that sleep is a critical aspect of health, there are very few guidelines that define what is meant by healthy sleep. In past research, the only national guideline on sleep that was identified came from Canadian health authorities that recommended “seven to 9 hours of good-quality sleep on a regular basis, with consistent bed and wake-up times.” 

One of the problems is that sleep is a complex biological process with several associated components. People who report suffering from sleep problems cannot all be lumped into the same category as there are different types of problems, with different causes, and not all of them may give rise to health issues. In general, however, previous research has found that getting too little sleep is associated with a higher risk of cardiovascular disease (CVD), although the role of other sleep issues, such as snoring, breathing difficulties and daytime sleepiness is not known. 

A new study, published in the journal BMC Medicine, has made use of data from over 300,000 middle-aged adults from the UK Biobank, who were 40 years old when they first registered their data, between 2006 and 2010. At that time, they answered questions relating to their sleep patterns as part of the initial survey. The study also used primary care data on clinical diagnoses of sleep issues, given to over 140,000 of these registered participants in the two years prior to the start of the Biobank study. 

Using these two complementary sources of data, the researchers aimed to estimate how many years of CVD-free life are lost by people who experience poor sleep.

As part of the baseline questionnaire, participants reported on five problematic sleep characteristics, based on which the researchers defined five healthy sleep characteristics, including having no usual insomnia complaints, getting adequate sleep (7 to < 9 h/day), not snoring, having a morning chronotype (early bird activity as opposed to night owl), and no frequent daytime sleepiness. 

The experts then scored participants from 0 to 5, according to their count of healthy characteristics and categorized them into three groups: “healthy sleep” (sleep score of ≥ 4); “intermediate sleep” (2 or 3 score); and “poor sleep” (≤ 1 score). At registration, 60 percent of the participants reported healthy sleep, while 38 percent and 2 percent reported intermediate and poor sleep, respectively.

The researchers noted all instances of CVD diagnoses and treatments in the subsequent years of participants’ lives (average follow up of 11 years), or until they died. In this time, 53,064 cases of CVD were diagnosed. They used statistical methods to determine the associations between sleep quality (or clinically diagnosed sleep disorder) and CDV-free life expectancy in the participants. 

The analysis revealed that different types of sleep disturbance are associated with different durations of compromised cardiovascular health later in life, when compared to healthy sleepers. In particular, men with clinical sleep-related breathing disorders lost nearly seven years of cardiovascular disease-free life compared to those without these conditions, and women with these conditions lost over seven years. 

Importantly, even general poor sleep, such as insufficient sleep, insomnia complaints, snoring, going to bed late, and daytime sleepiness, is associated with a loss of around two years of normal heart health in men and women.

“Anyone who’s had a few rough nights of sleep knows how it can lead to bad mood and not feeling one’s best. Our research shows that, over time, regular poor sleep can lead to significantly compromised cardiovascular health in middle and old age,” said study senior author Professor Emmanuel Stamatakis of the University of Sydney.

“Sleep apnea is well known to increase the risk of cardiovascular disease and other chronic conditions, but these findings are a wake-up call that poor sleep in general can pose significant risk to heart health,” he added.

While the additional life expectancy of 40-year-old women and men in the study was 39 and 38 years respectively, only 33 and 30 of these years (for women and men respectively) were expected to be free of CVD. However, women with poor sleep could expect only 31 additional years free of CVD while men who slept poorly could expect only 28 additional years free of CVD. This means that poor sleep characteristics, such as snoring and trouble falling asleep or staying asleep, can be warning signs of potential health issues in the future.

“While the average life expectancy of the UK study participants is around 80 years, people with clinically diagnosed sleep-related breathing disorders like sleep apnoea lost over seven years of cardiovascular-disease free life,” said study lead author Dr Bo-Huei Huang, an epidemiologist recently graduating from the Charles Perkins Centre and Faculty of Medicine and Health.

Professor Peter Cistulli, the ResMed Chair of Sleep Medicine at the Charles Perkins Centre and Royal North Shore Hospital, said that these findings are significant because they extend the findings of previous studies linking poor sleep to important health outcomes.

“Sleep is a vital biological function that has been under-appreciated in public health policy to date. It’s gratifying that these findings shine a light on the importance of sleep, and the need for it to be recognized as a pillar of good health, alongside physical activity and nutrition. The time is right to ensure that sleep is recognized in public health policy,” said Professor Cistulli.

The researchers conclude: “These results could lay the cornerstone for future research on early prevention against poor sleep and improving CVD-free life expectancy among poor sleepers. Especially, we hope that the current outcomes can serve as a reference for policymakers and professionals to develop national sleep guidelines.”

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By Alison Bosman, Earth.com Staff Writer

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