Literature Review

Less than 6 hours of sleep a night linked to serious, chronic illness



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 and Université Paris Cité found that beginning at age 50, those who slept 5 hours or fewer 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, said in an interview. Dr. Sabia is a researcher and epidemiologist at Université Paris Cité and INSERM in Paris, 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 in PLOS Medicine.

Risk of multiple chronic diseases

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, Dr. Sabia and her team asked nearly 8,000 civil servants in the United Kingdom 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, 1.30; 95% confidence interval, 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 with 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.

Dr. 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 functions, 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.


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