According to a large-scale meta-analysis published in GeroScience, people sleeping fewer than 7 hours a night face a 14% higher risk of death from all causes, while those who regularly sleep 9 hours or more increase their risk by 34% – compared to the optimal 7-8 hours of sleep per night.
The study by Semmelweis University comprised 79 international publications and data from more than 2.1 million participants in both short and long sleep groups.
The research also revealed significant differences between sex. Men who slept less than 7 hours had a 16% higher mortality risk, and those who slept 8 hours or more had a 36% increased risk. Women with short sleep durations had a 14% higher risk, while those with long sleep durations faced a 44% increased risk. These disparities may be related to hormonal, behavioural, or cardiovascular differences between men and women, though the exact mechanisms remain unknown.
Previous studies suggest that up to one-third of the global population experiences insomnia at some point in their lives, and approximately 10% are affected by chronic insomnia.
Sleep deprivation is a growing global health concern – the study warns. Millions of people around the world regularly sleep too little due to work demands, digital screen exposure, and stress. Shift workers and those with irregular schedules are particularly affected. Chronic sleep loss is associated not only with mortality but also with numerous health issues including obesity, diabetes, cardiovascular disease, and impaired immune function.
As a society, we are experiencing a sleep epidemic,
said Dr. György Purebl, Director of Semmelweis University’s Institute of Behavioural Sciences, co-author of the study. “Even though awareness has grown, our behaviour hasn’t changed much in the last decade. The constant exposure to blue light, pressure to remain available around the clock, and disruption of our natural biological rhythms continue to take a toll on our health.”
In a second study the Hungarian researchers focused on the relationship between sleep duration and stroke incidence and related mortality. Individuals sleeping 5-6 hours per night had a 29% higher risk of stroke and a 12% increase in stroke-related mortality. Those sleeping more than 8-9 hours had a 46% higher risk of stroke incidence and a 45% increase in stroke-related mortality.
“Stroke remains one of the leading causes of death and long-term disability worldwide,” said Dr. Balázs Győrffy, Head of the Department of Bioinformatics at Semmelweis University and senior author of both studies. “Identifying modifiable risk factors like sleep can offer powerful public health benefits. Our findings make it clear that sleep duration should be considered in stroke prevention strategies to reduce the burden on healthcare systems and improve population health.”
Each year, 15 million people suffer a stroke, according to the World Health Organization. Five million die, and another five million are left with long-term disabilities, often with vision or speech loss, paralysis, or cognitive impairment. Many cases could be prevented by managing blood pressure and avoiding smoking.
Improving sleep quality doesn’t always require radical changes. Experts recommend setting a consistent sleep schedule and creating a bedtime routine that includes limiting screen time and exposure to bright lights before bed. Keeping the bedroom dark, cool, and quiet, avoiding alcohol, limiting caffeine intake late in the day, and engaging in regular physical activity can also help support healthy, restorative sleep.
The meta-analyses were conducted as part of the Semmelweis Study, a long-term research project that will follow employees of Semmelweis University to examine how lifestyle factors like sleep impact health over time. The study aims to generate insights not only for internal health promotion, but also to inform recommendations for the general population through large-scale preventive strategies.
Photo: Boglarka Zellei – Semmelweis University; Cover photo: Envato Elements – artemp3
