Both insufficient and excessive sleep increase the risk of death and stroke, with those sleeping less than seven hours or more than nine hours a day facing significantly higher mortality rates—according to a comprehensive analysis by Semmelweis University published in GeroScience.
The study found that sleeping fewer than seven hours per night raises the risk of death by 14%, while sleeping nine hours or more increases that risk by 34%, compared to those who sleep the recommended 7–8 hours.
Semmelweis University researchers analyzed data from over 2.1 million adults through a meta-analysis of 79 international studies on short and long sleep durations. The results revealed significant gender differences: for men, sleeping less than seven hours increased mortality risk by 16%, and sleeping more than eight hours raised it by 36%. For women, the risks rose by 14% and 44%, respectively. Researchers suspect hormonal, behavioral, and cardiovascular factors may underlie these differences, though the exact causes are still unknown.
The most common sleep disorder identified in the study is chronic insomnia. Previous research shows that one in three people globally experience insomnia at some point, with around 10% suffering from it chronically.
The study’s authors warn that sleep deprivation is becoming a serious global public health issue. Millions of people sleep too little due to increased workloads, digital device use, and chronic stress. Particularly vulnerable are shift workers and those with irregular schedules. Long-term sleep deprivation is linked not only to increased mortality but also to conditions like obesity, diabetes, cardiovascular disease, and weakened immunity.
“We’re facing a sleep epidemic,” said Dr. György Purebl, Director of the Institute of Behavioural Sciences at Semmelweis University and co-author of the study. “Despite growing health awareness, our behavior hasn’t changed much in the past decade. Prolonged screen time, constant blue light exposure, 24/7 availability, and disrupted biological rhythms negatively affect our health,” he added.
In a related study, researchers examined the connection between sleep duration and stroke frequency and mortality. People sleeping 5–6 hours a night were 29% more likely to suffer a stroke, with a 12% higher risk of stroke-related death. For those sleeping more than 8–9 hours, the risk of stroke rose by 46%, and the risk of death by 45%.
“Stroke remains one of the leading causes of death worldwide and often results in long-term disability,” said Dr. Balázs Győrffy, head of the Bioinformatics Department at Semmelweis University and lead author of both studies. “Lifestyle factors like sleep are modifiable, offering a major public health opportunity. Sleep duration should be considered in stroke prevention strategies to ease healthcare burdens and improve population health.”
According to the World Health Organization, stroke affects 15 million people each year, of whom 5 million die and another 5 million suffer permanent impairments such as speech or vision loss, paralysis, or cognitive decline. Most strokes could be prevented by managing blood pressure and avoiding smoking.
Experts recommend establishing a consistent sleep routine, limiting screen use and bright light before bed, and ensuring a dark, cool, and quiet sleeping environment. Avoiding alcohol, moderating caffeine intake, and regular physical activity also contribute to restful sleep.
These meta-analyses are part of the ongoing Semmelweis Study, a long-term research project that tracks the health of university employees to examine how lifestyle factors—like sleep—affect health outcomes. The goal is not only to support institutional health promotion but also to help shape national public health recommendations.
(MTI)
