Sleep and Executive Function in Older Women: The Moderating Effect of Physical Activity

Background: Sleep and physical activity are both important for executive function; however, few cognitive function studies include comprehensive measurement of both of these behaviors. Understanding how physical activity impacts the associations between sleep and executive function in older women is especially pertinent given the high prevalence of sleep disturbances and longer life expectancies of women compared with men.

Purpose: To examine the independent and interactive associations of sleep and physical activity in relation to executive function in older women using both direct (i.e., device-based) and self-reported (i.e., diary) measurements.

Methods: A subset of 121 women, aged 73.3±1.7 years, in the Healthy Women Study wore an Actiwatch sleep monitor on their wrist and an ActiGraph accelerometer on their waist for 7-consecutive days. Additionally, participants kept sleep and physical activity diaries for the 7-day period. Executive function was measured with the Digit Symbol Substitution Test and the Trail Making Test B.

Results: Correlations between Actiwatch-assessed sleep efficiency and diary-reported sleep efficiency were modest (Spearman σ=0.19, p=0.04). In adjusted models, greater Actiwatch-assessed sleep efficiency was independently associated with more correct responses on the Digit Symbol Substitution Test (B=0.35, SE=0.15, p<0.02). Diary-reported sleep efficiency was not associated with executive function. A significant interaction (p<0.05) was observed between accelerometer-assessed physical activity and Actiwatch-assessed sleep efficiency in relation to executive function. Specifically, lower sleep efficiency was associated with poorer performance on executive function tasks among women with low levels of physical activity but not among women with high levels of physical activity.

Conclusion: Given the aging population, understanding both the risk and protective factors associated with the preservation of cognitive function in older adults is of great public health importance. Our findings suggest that greater levels of physical activity may attenuate the negative impact of poor sleep on executive function in older women, with the most robust effects observed using direct measurements of sleep and physical activity.

Supported by NIH grants R01 HL28266 and T32 HL07560