How sleep deprivation can harm your health

Adapted from  Improving Sleep , Medical Editor: Lawrence Epstein, MD, Instructor in Medicine, Harvard Medical School.

We all have trouble sleeping from time to time, but when insomnia persists day after day it can become a real problem. Insomnia becomes chronic when it happens at least three nights per week for three months or more, and may be caused by a medical or psychiatric problem.

Sleep is essential for the mind and body, which is why chronic sleep deprivation does more than leave you groggy — it can damage nearly every system in your body. From diabetes and high blood pressure to heart disease, mental illness, dementia, and weight gain, insufficient sleep disrupts critical hormonal and metabolic processes that keep you healthy. Below are some of the major health risks linked to poor sleep.

Diabetes. Sleeping just five to six hours a day doubles the risk of being diagnosed with prediabetes and type 2 diabetes compared to sleeping seven to eight hours a day, according to a 2021 review in the Journal of Endocrinology. As with overweight and obesity (which are also closely linked to type 2 diabetes), the underlying cause is thought to involve a disruption of the body’s normal hormonal regulation — in this case resulting from insufficient sleep.

High blood pressure. Sleeping less than seven hours a night raises the risk of high blood pressure, according to an analysis of data from over 700,000 people in two national health surveys. The association was especially strong among women and younger adults. People with very short sleep times (four or fewer hours per night) were twice as likely to have high blood pressure compared with those who slept seven hours nightly.

Heart disease. Chronic sleep deprivation is linked to many risk factors for heart disease, including unhealthy levels of cholesterol and triglycerides as well as high blood pressure. People who don’t get sufficient sleep also have higher blood levels of stress hormones and substances that indicate inflammation, a key player in cardiovascular disease. A 2022 study in Scientific Reports found that middle-aged people with a combination of sleep issues, including sleeping less than six hours per night, may have nearly three times the risk of heart disease.

Sleep apnea, one common cause of poor sleep, also raises heart disease risk. The low oxygen and high carbon dioxide levels that occur in apnea-disturbed sleep raise levels of stress hormones. This boosts blood pressure and heart rate and appears to increase the risk of heart attack, heart failure, and heart rhythm disorders such as atrial fibrillation. People with moderate to severe sleep apnea have three times the risk of stroke compared with people who don’t have the condition.

Mental illness. A study of about 1,000 adults ages 21 to 30 found that, compared with normal sleepers, people who reported a history of insomnia were four times as likely to develop major depression within the next three years. And two studies in young people — one involving 300 pairs of young twins, and another including about 1,000 teenagers — found thatlack of sleepoften preceded a diagnosis of major depression and (to a lesser extent) anxiety. Sleep problems in the teenagers preceded depression 69% of the time and anxiety disorders 27% of the time.

Dementia. Research increasingly links sleep disturbances to increased risk of developing dementia. A review of 18 studies, including a total of nearly a quarter-million people followed for an average of 9.5 years, found a link between lack of sleep and a higher risk of dementia. Experts believe that sleep helps clear the brain of amyloid, the protein thought to damage nerve cells in Alzheimer’s.

Weight gain. Numerous studies have linked inadequate sleep with obesity. A 2020 study in JAMA Internal Medicine provided further support for this connection. Researchers who analyzed two years of activity monitor data from more than 120,000 people found that shorter sleep duration was associated with higher body mass index. Lack of sufficient sleep disrupts hormones that control hunger and appetite. Excess weight, in turn, increases the risk of a number of health problems — including some of those listed above.

Getting enough sleep is one of the most important steps you can take to protect your health. The good news is that it’s never too late to start improving your sleep habits. Practicing good sleep hygiene, such as keeping a consistent bedtime, limiting screen time before bed, and creating a calm sleep environment, can make it easier to get the restorative rest your body needs.