Differential predictors of nighttime and daytime sleep complaints in older adults with comorbid insomnia and osteoarthritis pain

Objectives: Osteoarthritis (OA) is extremely common in older adults, affecting 50% of people aged 65 or older, and more than half of older adults with OA complain of significantly disturbed sleep. This study compared predictors of nighttime sleep complaints and daytime sleep-related consequences as measured by the Insomnia Severity Index (ISI) and Pittsburgh Sleep Quality Index (PSQI) in older adults with comorbid OA pain and insomnia.

Methods: A secondary analysis of baseline data from a large longitudinal randomized controlled trial. Multivariate regression analyses were performed to test two sets of predictive models.

Results: 367 older adults (mean age 72.9±8.2years; female 78.5%) with OA and insomnia were included in this analysis. In Model 1, fatigue and depression predicted daytime sleep-related consequences for both ISI and PSQI. When measures of sleep and pain beliefs/attitudes were added (Model 2), fatigue, and sleep and pain beliefs/attitudes predicted nighttime sleep complaints for both ISI and PSQI; depression was no longer a significant predictor of ISI daytime consequences, but remained in the model for PSQI daytime consequences.

Conclusions: This study found both similarities and differences in factors predicting nighttime sleep complaints and daytime sleep-related consequences. Individual beliefs/attitudes about sleep and pain were stronger predictors of sleep difficulties than were depression and pain. Fatigue was the strongest and most consistent predictor associated with both nighttime sleep complaints and daytime sleep-related consequences regardless of the scale used to measure these concepts.