Abstract
BACKGROUND AND OBJECTIVES: Sleep disorders often predict or co-occur with cognitive decline. Yet, little is known how the relationship unfolds among older adults at risk for cognitive decline.To examine the associations of sleep disorders with cognitive decline in older adults with unimpaired cognition, or impaired cognition (mild cognitive impairment [MCI] and dementia).
RESEARCH DESIGN AND METHODS: 5,822 participants (Mage=70) of the National Alzheimer's Coordinating Center database with unimpaired or impaired cognition were followed for three subsequent waves. Four types of clinician-diagnosed sleep disorders were reported: sleep apnea, hyposomnia/insomnia, REM sleep behavior disorder, or "other." Cognition over time was measured by the Montreal Cognitive Assessment (MoCA) or an estimate of general cognitive ability (GCA) derived from scores based on 12 neuropsychological tests.
Growth curve models were estimated adjusting for covariates. RESULTS: In participants with impaired cognition, baseline sleep apnea was related to better baseline MoCA performance (b=0.65, 95%CI=[0.07, 1.23]) and less decline in GCA over time (b=0.06, 95%CI=[0.001, 0.12]).
Baseline insomnia was related to better baseline MoCA (b=1.54, 95%CI=[0.88, 2.21]) and less decline in MoCA over time (b=0.56, 95%CI=[0.20, 0.92]). Furthermore, having more sleep disorders (across the four types) at baseline predicted better baseline MoCA and GCA, and less decline in MoCA and GCA over time.
These results were only found in those with impaired cognition and generally consistent when using self-reported symptoms of sleep apnea or insomnia. DISCUSSION AND IMPLICATIONS: Participants with sleep disorder diagnoses may have better access to healthcare, which may help maintain cognition through improved sleep.