• A study published in PLOS Medicine, including 30 years of data on 8 000 individuals, found an association between people who reported getting five hours of sleep or fewer every night at age 50 and an increased risk for chronic disease, like heart disease and diabetes.
• Experts suggest focusing on total weekly sleep, aiming for about 50 to 60 hours per week, so when you have a bad night of rest, you can sleep longer another day or add in a nap.

To some degree, the amount of sleep needed every night is individualised—one person may thrive on six hours while another requires nine to feel fully rested. But even with that flexibility, previous research indicates that getting too little sleep is problematic, and a new study suggests it may be especially harmful for those over 50.

Published in PLOS Medicine, the research looked at data spanning 30 years on nearly 8 000 men and women in the U.K. Sleep duration was measured six times in that timeframe, and researchers focused on data reported at age 50, 60, and 70.

They paid particular attention to the association between sleep duration and onset of a first chronic disease, such as diabetes, depression, liver disease, dementia, or heart failure.

How much sleep?

People who reported getting five hours of sleep or fewer at age 50 were 20 percent more likely to have been diagnosed with a chronic disease than those who slept more every night. The effects also stacked up as the years did: These participants were 40 percent more likely to be diagnosed with two or more chronic diseases later in life, compared to those who slept for seven hours nightly.

Researchers also assessed whether sleeping for a long duration of nine hours or more negatively affected health outcomes and didn’t find the same type of association. However, previous research suggests there may be a link between long sleep and poor health.

Although the results of these studies might imply that sleep duration itself is the cause of chronic illnesses, often it’s the opposite, according to W. Chris Winter, M.D., president of Charlottesville Neurology and Sleep Medicine, and author of The Sleep Solution.

“Shorter sleep can be an early warning system that something is going on with your health,” he told Bicycling. In many cases, it’s not that sleep is causing heart disease or diabetes, for example, but instead that problems with your cardiovascular or endocrine systems are reflected in your sleep patterns.

Sleep tends to change as we age, according to the National Institutes of Health, and many older people may have more difficulty falling asleep or they wake up more often during the night. But even with those variations, total sleep time can be maintained, Winter said. One helpful tip, he suggested, is to focus on weekly sleep amount rather than nightly. People tend to need between 50 to 60 hours of sleep per week, and if you have a few shorter nights, taking one or two naps that week or sleeping a little longer on other nights can help.

“Having a difficult night of sleep is part of the human existence,” said Winter. “Don’t think you’re doomed to have chronic disease because of it, especially if you’re older. You can make up for that lost time and still be healthy.”