Researchers at Columbia University in New York used data from roughly half a million people to link sleep length with signs of accelerated aging, and sleep specialist Saema Tahir weighed in on what the findings mean for everyday sleepers. The study, published in Nature, matched self-reported sleep times to 23 biological aging clocks to see whether organs and systems looked older or younger than someone’s chronological age. What follows is a clear, conversational look at the evidence, the limits of the research, and practical takeaways from the expert.

The team analyzed global biobank responses from about 500,000 people who reported how long they slept across a 24-hour period, including naps. Those self-reported durations were compared against multiple biological aging measures designed to estimate whether tissues and systems appear biologically older or younger. Using this broad dataset gave the researchers power to spot patterns across many health domains.

The headline result was a U-shaped relationship: both short and long sleep were tied to signs of older biology. Short and long sleepers tended to show higher biological age and an increased risk of future disease and death. In nine of the aging clocks the links reached statistical significance, with signals seen in the brain, heart, immune system and skin.

On the mortality front, the study found that short sleep was associated with about a 50% higher relative risk of all-cause death, while longer sleep carried roughly a 40% higher risk. The pattern of harms also differed: longer sleep showed stronger ties to psychiatric outcomes, whereas short sleep was more strongly connected to physical conditions such as cardiovascular, metabolic, musculoskeletal, neurological, pulmonary and gastrointestinal problems. Those contrasts suggest that how sleep goes wrong matters just as much as how much of it you get.

The study also gave sex-specific windows for the lowest biological age gap: women clustered around 6.5 to 7.8 hours and men around 6.4 to 7.7 hours. But the authors were careful to flag limitations: the sleep data were self-reported, and the study was observational. That means the work can point to associations without proving that sleeping a specific number of hours will slow or speed biological aging.

“Sleep is really when the body does its most critical repair work, including cellular restoration, immune regulation, hormonal balance, and even clearing out metabolic waste from the brain through what we call the glymphatic system,” said Saema Tahir, MD, who was not involved in the study. When those repair processes are consistently disrupted the damage accumulates at a cellular level and shows up as increased inflammatory markers and cellular changes that are “hallmarks of accelerated aging,” Tahir noted. “So, the relationship isn’t just correlational; there are real physiological mechanisms connecting poor sleep to the body aging faster than it should.”

Tahir cautions against treating the six- to eight-hour range as a one-size-fits-all prescription. “What I tell my patients is to use that range as a starting framework, but pay attention to how you feel,” she advised. “Are you waking up refreshed? Can you stay alert throughout the day without caffeine propping you up? Those functional cues matter just as much as the number on the clock.”

She also stressed that quantity is not the whole story. “I’ve seen patients who log seven hours but spend most of that time in light sleep, barely touching the deep slow-wave or REM stages that are most restorative,” Tahir said. “They age just as poorly, sometimes worse, than someone getting six hours of genuinely consolidated, high-quality sleep.” “So, chasing hours without addressing sleep fragmentation, sleep apnea or poor sleep architecture is missing the bigger picture,” she said. The takeaway from this study, according to Tahir, is that sleep is not a “lifestyle luxury,” but a “biological necessity with measurable consequences for how we age and how healthy we are.” “It doesn’t require a prescription or expensive intervention — it requires prioritization.”