Assessing The Bidirectional Relationship Between Physical Activity And Sleep In Elderly Women

A physically active lifestyle and quality sleep are associated with lower risk for obesity and cardiovascular disease. Cross-sectional studies demonstrate that greater physical activity (PA) is associated with better quality sleep. However, few studies have examined this relationship using objective measures. Additionally, few studies have examined the directionality of the relationship between daily variations in PA and nightly variations in sleep. Examining this association in elderly women has important public health significance given the co-occurrence of low PA levels with high prevalence of sleep disturbances in this population

Purpose To examine the bidirectional relationship between PA and sleep among elderly women using objective methods.

Methods A sub-group of participants [N=143, mean age= 73y] enrolled in the Healthy Women Study wore an ActiGraph accelerometer on their waist and an Actiwatch sleep monitor on their wrist concurrently for 7 consecutive days. Multi-level models examined whether average daily activity counts (ct·min·d-1) and moderate- to vigorous- intensity physical activity (MVPA; min·d-1) predicted Actiwatch-assessed sleep duration, sleep efficiency, and sleep fragmentation at night. Similar models were used to determine if nighttime sleep characteristics predicted PA the following day.

Results Higher average daily activity counts were associated with less sleep duration (β=-.04, p=.007), but not with sleep efficiency or fragmentation. Greater sleep efficiency was associated with higher average activity counts (β=.37, p=0.01) and MVPA (β=-.64, p=.009) the following day. Less sleep fragmentation was also associated with higher average activity counts (β=-.6, p=.02) and more MVPA (β=-.11, p=0.02) the following day. Findings were similar after adjustment for age, education, BMI, and depressive symptoms.

Conclusions Few studies have used objective measures to examine the temporal relationship between PA and sleep. These findings suggest that nightly variations in sleep efficiency influence PA the following day among elderly women; whereas, activity during the day influences sleep duration at night. Improving sleep quality among elderly women may be one way to encourage a physically active lifestyle. Supported by NIH grants R01 HL28266 and T32 HL07560