In a study of more than 86,000 adults in the United Kingdom, researchers found that longer and more irregular daytime naps were associated with a higher risk of death.
Participants were between 43 and 79 years old (baseline age = 63). Each wore an activity monitor for 7 days to track sleep patterns. Researchers at Massachusetts General Hospital/ Harvard Medical School analyzed nap duration, day-to-day variability, and nap timing across the day.
During a follow-up period of up to 8 years, 2,950 participants (3.4%) died. Among those, the average time from baseline to death was just over 4 years.
Longer naps were linked to a 20% higher risk of all-cause mortality per standard deviation increase in nap duration, even after adjusting for age, sex, body mass index, smoking, alcohol use, comorbidities, nighttime sleep duration, and chronotype. Greater variability in nap duration from day to day was associated with a 14% increased risk.
Timing of naps also mattered. Naps between 11 am and 1 pm or between 1 pm and 3 pm were associated with a 7% increase in mortality risk. Naps earlier or later in the day did not show significant associations.
On average, participants napped for 24 minutes per day, though duration varied. Researchers used a validated algorithm to detect naps from actigraphy data and applied transformations to correct for skewed distributions. Analyses accounted for individual differences in sleep patterns and biological rhythms.
All participants had no history of shift work, which can influence sleep behaviors and quality. The researchers emphasized that the study relied on objective sleep measurements rather than self-reports, which increased the reliability of the results.
The study did not investigate specific causes of death or whether naps themselves contributed directly to adverse outcomes. Rather, the results suggest that certain nap behaviors may reflect underlying health conditions or disruptions in daily routines.
The researchers suggested that tracking nap behavior with wearable devices may help identify health risks in older adults, and monitoring nap duration, timing, and consistency could offer additional tools for assessing well-being and guiding individualized care.
The study was funded by the Alzheimer’s Association and the American Academy of Sleep Medicine, and findings will be presented during the SLEEP 2025 annual meeting in Seattle.
Source: Sleep
