SLEEP DURATION, TIME IN BED, AND PHYSICAL FUNCTION DECLINE
Self-Reported Sleep Duration and Time in Bed as Predictors of Physical Function Decline: Results from the InCHIANTI Study
Sari Stenholm, PhD1; Erkki Kronholm, PhD2; Stefania Bandinelli, MD3; Jack M. Guralnik, MD, PhD4; Luigi Ferrucci, MD, PhD5
1National Institute for Health and Welfare, Department of Health, Functional Capacity and Welfare, Functional Capacity Unit, Turku, Finland; 2National Institute for Health and Welfare, Department of Chronic Disease Prevention, Population Studies Unit, Turku, Finland; 3Azienda Sanitaria di Firenze, Geriatric Unit, Florence, Italy; 4National Institute on Aging, Laboratory of Epidemiology, Demography, and Biometry, Bethesda, MD; 5National Institute on Aging, Clinical Research Branch, Baltimore, MD
To characterize elderly persons into sleep/rest groups based on their self-reported habitual total sleeping time (TST) and habitual time in bed (TIB) and to examine the prospective association between sleep/rest behavior on physical function decline.
Population-based InCHIANTI study with 6 years follow-up (Tuscany, Italy).
Men and women aged ≥ 65 years (n = 751).
Measurements and Results:
At baseline, participants were categorized into 5 sleep/rest behavior groups according to their self-reported TST and TIB, computed from bedtime and wake-up time. Physical function was assessed at baseline and at 3- and 6-year follow-ups as walking speed, the Short Physical Performance Battery (SPPB), and self-reported mobility disability (ability to walk 400 m or climb one flight of stairs). Both long (≥ 9 h) TST and long TIB predicted accelerated decline in objectively measured physical performance and greater incidence in subjectively assessed mobility disability, but short (≤ 6 h) TST did not. After combining TST and TIB, long sleepers (TST and TIB ≥ 9 h) experienced the greatest decline in physical performance and had the highest risk for incident mobility disability in comparison to mid-range sleepers with 7-8 h TST and TIB. Subjective short sleepers reporting short (≤ 6 h) TST but long (≥ 9 h) TIB showed a greater decline in SPPB score and had a higher risk of incident mobility disability than true short sleepers with short (≤ 6 h) TST and TIB ≤ 8 hours.
Extended time in bed as well as long total sleeping time is associated with greater physical function decline than mid-range or short sleep. TIB offers important additive information to the self-reported sleep duration when evaluating the consequences of sleep duration on health and functional status.
Stenholm S; Kronholm K; Bandinelli S; Guralnik JM; Ferrucci. Self-reported sleep duration and time in bed as predictors of physical function decline: results from the InCHIANTI study. SLEEP 2011;34(11):1583-1593.