To examine the associations of prevalent arthritis with systemic inflammation in older men and to test whether sleep health mediates the associations.
Cross-sectional data came from 2,562 community-dwelling older men (all were age 65 years or older; mean age 76 years) in the Osteoporotic Fractures in Men Study who participated in a sleep ancillary study in 2003-2005. Participants were classified as having osteoarthritis (OA) (24%) or rheumatoid arthritis (RA) (0.7%) based on self-reported diagnoses and medication use. We constructed a composite score of multidimensional sleep health (i.e., perceived sleep quality, sleepiness, frequency of daytime napping, wake after sleep onset, and sleep duration) measured by both self-report and actigraphy. We also created binary indicators of elevated inflammation using C-reactive protein (CRP) (>3 mg/liter) and interleukin-6 (IL-6) (>1.08 pg/ml) levels. Analyses controlled for age, diagnosed sleep disorders, body mass index, smoking status, relevant medication use, and comorbidities.
Older men with OA did not have higher risk of elevated CRP or IL-6 levels. However, indirect associations of OA through sleep health were found. OA was associated with poorer sleep health, which was further associated with 16% higher odds of elevated CRP (P < 0.001) and 12% higher odds of elevated IL-6 (P < 0.01) levels after controlling for OA. Older men with RA had higher odds of elevated CRP and IL-6 levels, but the associations were not mediated by sleep health.
Findings suggest that promoting sleep health may help reduce the risk of systemic inflammation in older men with OA.