Less Than 5 Hours of Sleep a Night Linked to Chronic Illness

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Individuals who are middle-aged and older and who sleep 5 hours or less a night may be at risk for an array of serious and chronic health conditions, ranging from heart disease to cancer, results of a large study show.

Researchers at University College London in the United Kingdom and Université Paris Cité, France, found that beginning at age 50, those who slept 5 hours or less a night had a 30% higher risk of developing multiple chronic diseases over time than those who slept at least 7 hours a night. By the time the participants were aged 70 years, that risk had increased to 40%.

Diseases for which there was a higher risk included diabetes, cancer, coronary heart disease, stroke, heart failure, chronic obstructive pulmonary disease, chronic kidney disease, liver disease, depression, dementia, Parkinson's disease, and arthritis.

"It is important to take care of our sleep," lead investigator Séverine Sabia, PhD, told Medscape Medical News. Sabia is a researcher and epidemiologist at Université Paris Cité and INSERM in Paris, France, and the University College London.

She noted that the source of the sleep problem must be addressed, but in cases in which there is no medical reason for sleep paucity, "healthy sleep habits are a must. These include keeping a regular sleep schedule, a healthy lifestyle — physical activity and light exposure during the day, and a light dinner — and avoidance of screens for a half hour before sleep."

The study was published online October 18 in PLOS Medicine.

Prior research suggests that sleeping for 5 hours or less or 9 hours or more is associated with cancer and cardiovascular disease (CVD).

For the current study, Sabia and her team asked nearly 8000 civil servants in the UK as part of the Whitehall II cohort study to report the amount of sleep they received beginning at age 50 every 4 to 5 years for the next 25 years. Study participants were free of chronic disease at age 50 and were mostly male (67.5%) and White (90%).

The investigators found that at age 50, those who slept 5 hours or less were 30% more likely to be diagnosed with multiple chronic diseases over time, (hazard ratio [HR] = 1.30; 95% CI: 1.12 – 1.50; P < .001) compared with their peers who slept 7 hours.

At age 60, those who slept 5 hours or less had a 32% greater risk of developing more than one chronic disease (HR = 1.32; 95% CI: 1.13 – 1.55; P < .001), and by age 70, this risk increased to 40% compared to their peers who slept 7 hours a night (HR = 1.40; 95% CI: 1.16 – 1.68; P < .001).

For participants who slept 9 or more hours per night, only those aged 60 (HR = 1.54, 95% CI: 1.15 – 2.06; P = .003) and 70 (HR = 1.51, 95% CI: 1.10 – 2.08; P = .010) were at increased risk of developing more than one chronic disease.

Sabia noted that previous studies have shown that those who slept less than 5 hours a night were more likely to develop diabetes, hypertension, CVD, or dementia. "However, chronic diseases often coexist, particularly at older ages, and it remains unclear how sleep duration may be associated with risk of multimorbidity," she said. She noted that several biological hypotheses have been proposed as underlying the association.

"Sleep is important for the regulation of several body function, such as metabolic, endocrine, and inflammatory regulation over the day, that in turn, when dysregulated, may contribute to increased risk of several chronic conditions."

The authors acknowledge several study limitations, including the fact that the data were obtained via participant self-reports, which may be affected by reporting bias. There was also a lack of diversity within the study sample, as the civil servants were mostly male and White. In addition to this, the investigators note that the study population of British civil servants tended to be healthier than the general population.

Commenting on the findings for Medscape Medical News, Charlene Gamaldo, MD, urged caution in interpreting the findings. She noted that self-reporting of sleep has been established as "potentially problematic" because it doesn't always correlate with actual sleep.

Gamaldo, who is professor of neurology and psychiatry at Johns Hopkins University in Baltimore, Maryland, and is the medical director of the JHU Center for Sleep and Wellness, said previous studies have shown that underestimation of sleep can occur among those suffering with insomnia and that overestimation can be seen among individuals with behaviorally based chronic, insufficient sleep.

Gamaldo also raised the issue of sleep quality.

"Getting 5 hours of high-quality sleep is less worrisome than one getting 8 hours of terrible-quality, based on untreated sleep apnea, for instance," she noted.

In addition, she pointed out that chronic health problems can interrupt sleep. "Which is the chicken, and which is the egg?" she asked.

"For me, the take-home of current literature and supported by this paper is that individuals with sleep quality complaints, short duration, or related impact in daytime function should address them with their treating provider to assess for the underlying cause.

"Those sleeping under 5 hours without complaints should consider whether 5 hours really represents the amount of sleep they need to wake rested and function at their best. If answer is no, they should prioritize getting more sleep," she concluded.

The study was funded by the National Institute on Aging, the National Institute of Health, the UK Research Medical Council, the British Heart Foundation, the Wellcome Trust, and the French National Research Agency. The investigators and Galmaldo report no relevant financial relationships.

Eve Bender is a Pittsburgh-based medical journalist who began working for Medscape Medical News in October 2022. Before that, she wrote for Psychiatric News, Neurology Today, and MedPage Today.

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