Short-term improvement in insomnia symptoms predicts long-term improvements in sleep, pain, and fatigue in older adults with comorbid osteoarthritis and insomnia.
In a primary care population of 367 older adults (aged ?60 years) with osteoarthritis (OA) pain and insomnia, we examined the relationship between short-term improvement in sleep and long-term sleep, pain, and fatigue outcomes through secondary analyses of randomized controlled trial data. Study participants, regardless of experimental treatment received, were classified either as improvers (?30% baseline to 2-month reduction on the Insomnia Severity Index [ISI]) or as nonimprovers. After controlling for treatment arm and potential confounders, improvers showed significant, sustained improvements across 18 months compared with nonimprovers in pain severity (P<0.001, adjusted mean difference=-0.51 [95% CI: -0.80, -0.21), arthritis symptoms (P<0.001, 0.63 [0.26, 1.00]), and fear avoidance (P=0.009, -2.27 [-3.95, -0.58]) but not in catastrophizing or depression. Improvers also showed significant, sustained improvements in ISI (P<0.001, -3.03 [-3.74, -2.32]), Pittsburgh Sleep Quality Index Total (P<0.001, -1.45 [-1.97, -0.93]) and general sleep quality (P<0.001, -0.28 [-0.39, -0.16]) scores, Flinders Fatigue Scale (P<0.001, -1.99 [-3.01, -0.98]), and Dysfunctional Beliefs About Sleep Scale (P=0.037, -2.44 [-4.74, -0.15]), but no improvements on the Functional Outcomes of Sleep Questionnaire or the Epworth Sleepiness Scale. We conclude that short-term (2-month) improvements in sleep predicted long-term (9- and 18-month) improvements for multiple measures of sleep, chronic pain, and fatigue. These improvements were not attributable to nonspecific benefits for psychological well-being, such as reduced depression. These findings are consistent with benefits of improved sleep for chronic pain and fatigue among older persons with osteoarthritis pain and comorbid insomnia if robust improvements in sleep are achieved and sustained.