Personalized Definition of Short Sleep Using Long-Term Wearable Sleep Distributions
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Study Objectives
To evaluate a framework using wearable data to personalize the definition of ‘short sleep’, comparing its temporal and functional characteristics against a fixed threshold.
Methods
462 healthy adults wore sleep trackers and provided daily ecological momentary assessments for a year. Short sleep was defined using either a fixed threshold of <6 h/night (fSS) or personalized thresholds anchored to individual sleep-duration distributions (pSS). Temporal patterns of consecutive short-sleep nights were characterized. Linear mixed-effects models examined associations between accumulating short-sleep nights and short- and long-term markers. Sleep patterns across six other countries were also evaluated.
Results
pSS and fSS produced similar average thresholds and overall prevalence of short-sleep nights. However, pSS showed larger effect estimates for short-term outcomes, including alertness, sleep satisfaction, stress, sleep heart rate, HRV, and sedentariness. Effects increased with successive short-sleep nights. Proportion of pSS showed stronger association with blood pressure and arterial stiffness. Isolated short nights were common, whereas longer runs were uncommon and typically followed by incomplete recovery sleep. Personalized thresholds distinguished stable short sleepers with few pSS nights from individuals experiencing recurrent sleep shortfall and highlighted vulnerability among those achieving ‘recommended’ sleep duration but with high variability. Despite marked cross-country differences in sleep habits, the distribution of short-sleep runs, and termination patterns were remarkably similar.
Conclusion
Anchoring short sleep to an individual’s habitual sleep distribution captures relative sleep shortfall beyond absolute duration, better characterizing the functional impact of ‘short’ sleep. Preventive strategies may benefit from limiting pSS accumulation together with addressing sporadic inadequate sleep.
Statement of Significance
Evidence describing how short sleep occurs under real-world conditions remains limited. Using long-term wearable recordings, we show that isolated short nights are common whereas extended runs are uncommon and typically followed by recovery sleep. We evaluated a personalized definition of inadequate sleep anchored to individual habitual sleep patterns rather than a fixed duration threshold. This framework more sensitively captured short-term functional impairments involving alertness, stress, sleep satisfaction, autonomic function and sedentariness. Stronger associations with longer-term vascular risk markers were also observed. Personalized wearable-derived metrics may provide a scalable approach to individualizing sleep planning without undue emphasis on occasional short sleep.
