Sleep Disturbances predict cognitive decline in cognitively healthy adults

Abstract

AbstractBackgroundSleep disturbances, including insomnia, poor sleep quality, and sleep fragmentation, are implicated in the development and progression of Alzheimer’s disease and related dementias in older adults. However, the effect of sleep disturbances on lifespan in those with cognitive impairment has not been studied independently from other neuropsychiatric symptoms such as disinhibition. The purpose of this study was to determine if sleep disturbances predict increased risk of earlier mortality across cognitive status (e.g., normal, mild cognitive impairment [MCI] and dementia) and risk of mortality independent from other neuropsychiatric symptoms known to predict dementia.MethodThe National Alzheimer’s Coordinating Center database was used to evaluate the mortality risk conferred by nighttime behaviors as determined by the neuropsychiatric inventory questionnaire (NPI‐Q). The effect of nighttime behaviors was used as a surrogate for sleep disturbances at the participant’s baseline assessment. Based on previous work, cognitive status was stratified by normal cognitive, MCI, and dementia using Montreal Cognitive Assessment scores. Covariates of age, sex, education, race, and other NPI‐Q items on mortality risk were analyzed using Cox regression.ResultThe sample was comprised of 31,288 participants, of whom 10,329 (33%) died during follow‐up and lasted a median [interquartile range] of 56.5 [30.2 – 88.8] months for deaths and 39.5 [23.1 – 75.1] months for survivors. One‐fifth of patients (n = 6509) experienced nighttime behaviors (e.g., nighttime awakenings). Worse cognitive status, older age, female sex, lower education, and increased neuropsychiatric burden increased mortality risk (ps≤.02). However, when explored independently, nighttime behaviors were found to predict earlier mortality (hazard ratio [HR]: 1.11 95% CI: [1.06,1.16], p<.001).ConclusionFindings expand on current evidence that the cross‐sectional prevalence of sleep disturbances increases with worsening cognition. Sleep disturbances predicted a higher risk of mortality while controlling for other variables. Potential mechanisms by which sleep disturbances may play a role in cognitive impairment or earlier mortality should be explored, including circadian rhythm disturbances and alteration in homeostatic and motivational processes.