Sleep quality and cognitive decline in a community of older adults in Daqing City, China

Objectives: To examine the association between self-reported sleep quality and cognitive decline one year later. Patients/Methods: A longitudinal study of 1010 cognitively intact adults, aged 65-80 years at baseline, from two urban communities in China was performed. Sleep quality at baseline was measured using the Pittsburgh Sleep Quality Index (PSQI). Cognitive function was determined by using the Chinese version of Mini-Mental State Examination (CMMSE) at the baseline and one year later. Substantial CMMSE decline was defined as the CMMSE score decreases by three or more points during the follow-up. Potential confounders, such as age, sex, education, baseline CMMSE score, depression, physical activity level, drinking status, smoking status, body mass index, snoring frequency, history of hypertension, diabetes, and coronary heart disease were measured via questionnaires or physical examination. Results: After adjusting for potential confounders, individuals with poor sleep quality (PSQI > 7), relative to whose with good sleep quality, had 0.32 (95% CI: -0.62, -0.02; p = 0.04) CMMSE-points more decline and tended to have a higher likelihood of developing substantial CMMSE decline (OR = 1.46; 95% CI: 0.97, 2.18; p = 0.06). Among seven subscales of the PSQI, poor sleep efficiency was associated with greater CMMSE decline (beta = -0.16, 95% CI: -0.29, -0.03; p = 0.01) and higher risk of substantial CMMSE decline (OR = 1.24, 95% CI: 1.05, 1.46; p = 0.01). Short sleep duration (sleeping ≤5 h/night) was also significantly associated with more CMMSE decline and a higher likelihood of developing substantial CMMSE decline (p < 0.05 for both). Conclusions: Self-reported poor sleep quality may be an indicator of early cognitive decline for elderly people and should be paid particular attention by clinicians.