Five hours is the minimum: Anyone who sleeps less than five hours at night is harmful to their health. Because then the risk increases by 30 to 40 percent to develop more than one chronic disease – from cardiovascular diseases to diabetes and cancer to dementia. Adequate sleep is particularly important in middle and older age from 50 years. At this age, it should be seven to eight hours of sleep at night, as the researchers explain.
Sleep is essential for our survival: our brain needs the break to flush out waste, to close synapses recalibrate and to save what has been learned, the body uses this phase for regeneration. If we don’t sleep, we become more irritable, more sensitive to pain, less concentrated and tend to have falsified memories. Persistent lack of sleep can with children even have a lasting impact on brain development, increasing the risk of cardiovascular disease in adults.
Risk for chronic diseases in focus
But when is too little sleep harmful to your health? Séverine Sabia from the University of Paris and her colleagues investigated this using a long-term study with a good 7,800 participants. Over a period of 25 years, the initially 50-year-old test subjects were regularly asked about their average nightly sleep duration and medically examined.
A particular focus was on an accumulation of chronic diseases, the so-called multimorbidity. “Multimorbidity is increasing in industrialized countries, more than half of older adults already have at least two chronic diseases,” explains Sabia. The role of sleep in this tendency to high blood pressure, arteriosclerosis, diabetes, cancer, dementia, arthritis and chronic liver or kidney disease has not yet been clarified.
Five hours is the minimum
The evaluation of the long-term data showed that those over the age of 50 who only sleep five hours or less at night have a 20 percent higher risk of developing a first chronic disease in the years and decades to come compared to those who sleep seven or eight hours. If the lack of sleep continues, the risk of a second chronic disease increases to 40 percent, as the team determined.
The same applies to older people aged 60 or 70: Their risk of multimorbidity increases by 30 to 40 percent if they only sleep five hours or less per night over a long period of time. “Our results thus show a connection between insufficient sleep duration and the development of multiple chronic diseases,” report Sabia and her colleagues. This relationship applies to both middle-aged and older people.
Too much sleep is also not good
The researchers also examined the extent to which a particularly long night’s sleep of nine hours or more affects health. However, there was no added value for middle-aged people. In older people who already suffer from a chronic disease, on the other hand, a particularly long sleep often indicates poorer sleep quality and an increased risk of further diseases, as the team determined.
“The recommendation is to sleep around seven to eight hours a night – sleeping more or less increases the risk of chronic diseases,” explains Sabia. “To improve your night’s sleep, you should practice good sleep hygiene: keep your bedroom dark and at a good temperature, stop eating large meals before bed, and avoid electronic devices.” Getting enough exercise and fresh air during the day can also improve sleep quality . (PLoS Medicine, 2022; doi: 10.1371/journal.pmed.1004109)
Those: University College London