Sleep Variability and Inflammation in Midlife and Older Women

Objective Shorter sleep duration and more sleep disturbances, in addition to greater night-to-night fluctuations in sleep (intraindividual variability; IIV), have been associated with elevated inflammation. However, these associations were only at the between-person level. The current study examined the within-person relationship between mean levels and IIV of sleep duration and sleep disturbances and C-reactive protein (CRP) in healthy, aging women. Methods Participants (N = 179) from a longitudinal study of activity and well-being in middle-aged and older women (mean age = 62 years; range = 50-75 years) completed a 7-day daily diary, every 3 months, for 2 years (up to nine bursts). Sleep was assessed each day asking participants how many hours of sleep they got the night before and with the four-item PROMIS Sleep Disturbance Short Form. Finger-stick dried blood spot samples were collected after each 7-day daily diary. Results In bursts when women experienced greater than average variability in sleep duration, they had higher CRP (γ = 0.06, p =.004). Within-person changes in mean sleep duration were not associated with CRP. In addition, neither mean sleep disturbances nor sleep disturbance IIV were associated with CRP. Conclusions This study is the first to show that within-person changes in variable sleep duration are related to changes in inflammation. Findings from the current study suggest that greater variability in sleep duration is related to higher CRP, which may increase risk for early morbidity and mortality. Future studies should investigate inflammation as a pathway linking sleep variability and health.