Associations between Objectively Measured Physical Activity, Sedentary Behaviour and Time in Bed among 75+ Community-dwelling Danish Older Adults
Li-Tang Tsai, Eleanor Boyle, Jan Brønd, Gry Kock, Mathias Skjødt, Lars Hvid, Paolo Caserotti
BMC Geriatrics, 21, Article number: 53 (2021)
Background and Method
Older adults are recommended to sleep 7-8 hours/day. Time in bed (TIB) differs from sleep duration and includes also the time of lying in bed without sleeping. This study was based on cross-sectional analysis of the Healthy Ageing Network of Competence (HANC Study). Physical activity and sedentary behaviour were measured by a tri-axial accelerometer (ActiGraph) placed on the dominant wrist for 7 days. TIB was recorded in self-reported diaries and participants were categorized as “usually”, “sometimes”, or “rarely” meeting the recommended TIB of 7-9 hr/night in the measurement period, corresponding to “≥80%”, “20-79%”, and “<20%” of measurement days, respectively.
Results and Conclusion
341 older adults (median age 81 (IQR 5), 62% women) were included with median TIB of 8hr 21min (IQR 1hr 10min)/day, physical activity level of 2054 (IQR 864) counts per minutes (CPM)/day with 64% (IQR 15%) of waking hours in sedentary behavior. Those who are more active (with average CPM within the highest tertile) are less likely to be categorized as “rarely” complying to 7-9hr TIB (67 % lower risk) when compared to those who are less active (CPM within the lowest tertile of average CPM). Being highly sedentary (≥10 hr/day of sedentary behavior) resulted in over 3 times higher risk to be categorized as “rarely” complying to 7-9hr TIB (relative risk ratio 3.21 (1.50-6.88), p=0.003). For older adults, being physically active and less sedentary was associated with being in bed for 7-9 hours/night for most nights (≥80%). Practical implication of this study is to recommend older adults to be in bed for preferably 7 to 9 hours per night. In order to achieve this goal, clinicians can recommend evidence-based strategies to older adults for promoting adequate TIB and improving sleep quality. Future longitudinal studies are warranted to explore the causal relationship between physical activity, time in bed, and sleep duration. Lower sensitivity of wrist-worn accelerometers to distinguish physical activity at higher intensities needs to be considered and perhaps replaced or coupled with measures from thigh-worn or hip-worn accelerometers.