Objective. To evaluate sleep quality in women with hip pain due to daily activities involving the lower extremity joints. Methods. We evaluated the association of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) hip pain severity score with objective sleep measures obtained by wrist actigraphy in 2,225 white women ≥65 years of age enrolled in the Study of Osteoporotic Fractures. Results. Women had an increased odds of spending ≥90 minutes awake after sleep onset (odds ratio [OR] 1.28, 95% confidence interval [95% CI] 1.11-1.50) for every 5-point increase in hip pain score after adjustment for all covariates. Hip pain when sitting or lying was the strongest predictor of sleep fragmentation (OR 2.0, 95% CI 1.47-2.73); however, standing pain was associated with a higher number of awake minutes in bed scored from sleep onset to the end of the last sleep episode, independent of pain while in bed (OR 1.41, 95% CI 1.07-2.01). Sleep disturbances increased significantly after the first 2 hours of sleep in women with severe hip pain compared to those without hip pain (mean ± SD 1.4 ± 0.47 minutes per hour of sleep; P < 0.003). Similar associations were observed for long wake episodes >5 minutes. There were no associations between daytime napping, sleep latency, sleep efficiency, and total sleep minutes and WOMAC hip pain. Conclusion. Fragmented sleep was greater in women with hip pain compared to those without hip pain; however, fragmented sleep in women with severe hip pain compared to those without hip pain was unchanged until after the first 2 hours of sleep. Further investigations into pain medications wearing off over time or the prolonged periods of inactivity decreasing the pain threshold are warranted.
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