Both underestimation and overestimation of sleep duration linked to higher mortality in older men with sleep disturbances
New research finds that how accurately older men perceive their own sleep time may matter as much for survival as how long they actually sleep.
Lead
A large longitudinal study published in Scientific Reports has found that older men with sleep disturbances who either significantly underestimate or overestimate how long they sleep face a substantially higher risk of death over the following decade compared to those whose perceived sleep duration aligns closely with objective measurement. The findings suggest that the discrepancy between subjective and objective sleep time, long known as a feature of insomnia, may itself carry independent prognostic value for mortality.
Researchers from the National Center of Neurology and Psychiatry in Tokyo and collaborating institutions analyzed data from 813 older male participants in the Osteoporotic Fractures in Men (MrOS) Sleep Study, all of whom reported clinically significant sleep disturbances indicated by a Pittsburgh Sleep Quality Index score above 5. Participants who used medications known to affect sleep perception or sleep duration were excluded from the analysis.
What they found
The study used a metric called the Misperception Index (MI), calculated as the difference between self-reported total sleep time and objectively measured total sleep time from wrist actigraphy. Participants were divided into quartiles based on their MI scores. Those in the highest quartile (high MI) were classified as “underestimators”: they reported sleeping substantially less than they actually did. Those in the lowest quartile (low MI) were classified as “overestimators”: they reported sleeping more than objective measures indicated. The middle two quartiles served as the reference group.
Over a median follow-up of 11.9 years, 502 of the 813 participants died (61.7 percent). After adjusting for demographic factors, health status, and sleep-related variables, both ends of the misperception spectrum were associated with significantly elevated mortality risk.
Underestimators had a 26 percent higher risk of death compared to the reference group (hazard ratio 1.26; 95 percent confidence interval 1.01 to 1.58). Overestimators fared even worse, with a 42 percent higher risk (HR 1.42; 95 percent CI 1.13 to 1.78). The associations held after controlling for objective sleep duration, sleep efficiency, and other confounding variables, suggesting the discrepancy itself, not merely sleep duration, was driving the relationship.
The study’s authors, led by Tomohiro Utsumi, noted that the misperception index may serve as a useful clinical marker for identifying older adults at elevated mortality risk. “These measures may be useful for risk assessment in clinical settings,” they wrote.
Why it matters
Sleep misperception (the gap between how long people think they sleep and how long they actually sleep) has been a long-standing puzzle in sleep medicine. It is particularly common among people with insomnia, who often report sleeping far less than objective measurements show. This study is among the first to demonstrate that both underestimation and overestimation carry independent mortality risk in a large, well-characterized cohort with sleep disturbances tracked over more than a decade.
The finding that overestimators faced an even higher risk than underestimators may be especially important. Overestimation of sleep duration could reflect a different underlying pathology, possibly related to deficits in interoceptive awareness, subtle neurological changes, or a blunted perception of wakefulness that may signal broader physiological decline. The study did not examine mechanisms directly, but the differential risk profiles suggest that under- and overestimation may not be simple opposites on a single continuum.
Clinically, the results imply that asking patients how long they think they sleep, and comparing that to objective measures when feasible, could yield information beyond what either measure alone provides. For older men reporting sleep disturbances, a large mismatch in either direction might warrant closer attention to overall health status and mortality risk.
Limits
The study has several important limitations. The sample was restricted to older men (mean age approximately 76 years), so the findings may not generalize to women, younger populations, or individuals without sleep disturbances. Although the authors adjusted for numerous potential confounders, residual confounding cannot be ruled out in observational research.
The study also did not investigate the biological pathways linking sleep misperception to mortality. Possible mechanisms include dysregulation of the autonomic nervous system, chronic low-grade inflammation, or neurodegenerative processes that affect both sleep perception and survival, but these remain speculative.
Additionally, some of the study authors disclosed potential competing interests, including honoraria or consulting fees from pharmaceutical companies such as Eisai, MSD, and Daiichi Sankyo. While the research itself was independent and peer-reviewed, readers should be aware of these disclosures when evaluating the findings.
Bottom line
Both underestimation and overestimation of sleep duration, as measured by the discrepancy between self-reported and actigraphy-derived sleep time, independently predict higher all-cause mortality in older men with sleep disturbances. The misperception index may offer a simple, clinically accessible tool for risk stratification in this population, though further research is needed to establish causal pathways and confirm generalizability to other groups.
Source
Utsumi T, Yoshiike T, Aritake-Okada S, et al. Both underestimation and overestimation of sleep duration predict mortality in older men with sleep disturbances. Scientific Reports. Published online June 27, 2026. doi:10.1038/s41598-026-60004-z