Associations between longitudinal trajectories of insomnia symptoms and sleep duration with objective physical function in postmenopausal women: the Study of Women's Health Across the Nation.

STUDY OBJECTIVES Examine the association between trajectories of self-reported insomnia symptoms and sleep duration over 13 years with objective physical function. METHODS We utilized data from 1627 Study of Women's Health Across the Nation (SWAN) participants, aged 61.9±2.7 y at the end of the 13-y follow-up. Latent class growth models identified trajectories of insomnia symptoms (trouble falling asleep, frequent night-time awakenings, and/or early-morning awakening) and sleep duration over 13 y. Physical function tests were performed at the end of the 13-y period: 40-ft walk, 4-m walk, repeated chair stand, grip strength, and balance. Multivariable regression analyses examined each physical function measure according to the insomnia symptom or sleep duration trajectory group. RESULTS Five insomnia symptom trajectories and two sleep duration trajectories were identified. Women with a consistently high likelihood of insomnia symptoms and women with a decreased likelihood of insomnia symptoms (i.e., improving) had slower gait speed (3.5% slower 40-ft walk [consistently high], 3.7% slower 4-m walk [improving]; each P≤.05) than those with a consistently low likelihood of insomnia symptoms. In contrast, women with a steep increase in the likelihood of insomnia symptoms over time and women with persistent insufficient sleep duration had lower odds of having a balance problem (odds ratio [OR]=0.36 and OR=0.61, respectively; each P<.02) compared to those with a consistently low likelihood of insomnia symptoms and those with persistent sufficient sleep duration, respectively. CONCLUSION These results suggest that women's sleep during midlife has important implications for maintaining physical function during the transition into older adulthood.