Good quality sleep is essential for good health. More and more research is looking at how sleep duration affects wellbeing and the development of disease. Research led by UCL researchers concludes that less than five hours of sleep in mid to late life may be associated with an increased risk of developing at least two chronic diseases. The study, published in PLOS Medicine, analyzed the impact of sleep duration on the health of more than 7,000 men and women aged 50, 60 and 70 from the Whitehall II cohort study.

Short Sleep Duration and Multimorbidity

The researchers investigated the relationship between the sleep duration of individual participants, mortality and whether they had been diagnosed with two or more chronic diseases (multimorbidity) – such as heart disease, cancer or diabetes – over the course of 25 years. People who reported sleeping five hours or less at age 50 were 20% more likely to have been diagnosed with a chronic disease and 40% more likely to have been diagnosed with two or more chronic diseases over 25 years than those who slept up to seven hours. In addition, sleeping five hours or less at ages 50, 60 and 70 was associated with a 30 to 40% increased risk of multimorbidity compared to people who slept up to seven hours.

The researchers also found that a sleep duration of five hours or less at age 50 was associated with a 25% increased risk of death over the 25 years of follow-up – which can mainly be explained by the fact that a short sleep duration increases the risk of chronic diseases, which in turn increase the risk of death.

Multimorbidity is increasing in high-income countries and more than half of older adults now have at least two chronic diseases. This poses a major public health challenge, as multimorbidity is associated with high utilization of healthcare services, hospitalization and disability. As people get older, their sleeping habits and sleep patterns change. However, it is recommended to sleep 7 to 8 hours per night, as sleep duration above or below this has been associated with individual chronic diseases in the past.

The Effects of a Long Sleep Duration

To ensure a better night’s sleep, it is important to maintain good sleep hygiene, e.g. ensuring that the bedroom is quiet, dark and at a comfortable temperature before going to bed. It is also advisable to turn off electronic devices and avoid large meals and stimulant drinks before bedtime. Physical activity and exposure to light during the day and relaxation exercises before going to bed can also promote a good night’s sleep.

As part of the study, the researchers also investigated whether a long sleep duration of nine hours or more has an effect on health. There was no clear link between a long sleep duration at the age of 50 and multimorbidity in healthy people. However, if the participants had already been diagnosed with a chronic disease, a long sleep duration was associated with an approximately 35% increased risk of developing another disease. The researchers suspect that this could be due to underlying health conditions that affect sleep.

Getting enough sleep allows the body to rest. There are a number of other ways in which poor sleep can increase the risk of heart disease or stroke, including increased inflammation and elevated blood pressure. This study adds to a growing body of research that emphasizes the importance of a good night’s rest.

Study Limitations

The researchers relied on self-reports of sleep, which are likely to be subject to bias, although data from 4,000 participants whose sleep was measured using an electronic device corroborates the findings. Data on sleep quality was only available for 60- and 70-year-olds. The Whitehall II study included only civil servants, all of whom were working at the time of recruitment to the study and were likely to be healthier than the general population.