Sleeping less than seven hours a night is one of the main predictors of lower life expectancy in the United States, second only to smoking, according to a national study published in the journal SLEEP Advances.

The research, led by Andrew McHill, associate professor at Oregon Health & Science University (OHSU), analyzed data from all US states between 2019 and 2025 and found a consistent correlation between insufficient sleep duration and a shorter life, even when considering other risk factors such as diet, exercise and loneliness.

The magnitude of the association between insufficient sleep and the risk of premature death surprised the researchers themselves. “I didn’t expect it to be so strongly correlated with life expectancy,” McHill said.

The analysis, conducted primarily by graduate students in OHSU’s Sleep, Chronobiology and Health Laboratory, used a national database that linked average life expectancy by county to Centers for Disease Control and Prevention (CDC) surveys on sleep habits.

The results showed that, year after year and in almost all states, sleeping less than seven hours is associated with a meaningful reduction in longevity.

When comparing sleep with other behavioral factors, the study found that lack of sleep ranked as the second strongest predictor of lower life expectancy after smoking when examining county-level data from 2019 to 2025, ahead of physical inactivity and diabetes.

The researchers highlighted that the relationship was maintained even when statistically controlling for these other factors, wich reinforces the relevance of sleep as a fundamental pillar of public health. The research was supported by the National Heart, Lung, and Blood Institute of the US National Institutes of Health.

The definition of sufficient sleep used in the study is based on recommendations from the CDC, the American Academy of Sleep Medicine, and the Sleep Research Society: at least 7 hours per night.

McHill emphasized the importance of meeting this threshold: “People should really strive to get between seven and nine hours of sleep if possible,” he said in a statement from the University of Oregon. This advice is especially relevant given the prevalence of insufficient sleep in the American population, a problem that, according to the authors, requires priority attention.

The implications for public health are clear. McHill and his team urge you to consider sleep as seriously as diet or exercise.

The study suggests that treating sleep as a luxury or something dispensable can have direct consequences on longevity and quality of life, which is why they recommend policies and campaigns that promote healthy sleep habits in the population.

Why does lack of sleep affect life expectancy?

The study acknowledges that while previous research has linked lack of sleep to increased mortality, this is the first time an annual, county-level correlation has been documented across the United States, reinforcing