Sleep-disordered breathing, sleep quality, and mild cognitive impairment in the general population

There is increasing evidence that sleep disorders are associated with cognitive decline. We, therefore, examined the cross-sectional association of sleep-disordered breathing (SDB), sleep quality, and three types of sleep complaints (difficulties initiating sleep, difficulties maintaining sleep, and early morning awakening) with mild cognitive impairment (MCI) and its subtypes. A group of 1,793 participants (51% men; 63.8 ± 7.5 years) of the population-based Heinz Nixdorf Recall study (total sample n = 4,157) received a screening for SDB and self-report measures of sleep complaints. Group comparisons were used to compare performances among five cognitive subtests. Multivariate logistic regression models were calculated to determine the association of MCI (n = 230) and MCI subtypes (amnestic MCI, n = 120; non-amnestic MCI, n = 110) with SDB severity levels, poor sleep quality, and sleep complaints. Severe SDB (apnea-hypopnea index ≥30/h, n = 143) was not associated with MCI, amnestic MCI, or non-amnestic MCI. Poor sleep quality was associated with MCI (Odds ratio (OR) = 1.40, 95% confidence interval (CI) = 1.02-2.03; fully adjusted) as well as frequently reported difficulties initiating sleep (OR = 1.94, 1.20-3.14), difficulties maintaining sleep (OR = 2.23, 1.27-4.63), and early morning awakening (OR = 2.30, 1.32-4.00). Severe difficulties initiating sleep (OR = 2.23, 1.21-4.13) and early morning awakening (OR = 2.88, 1.45-5.73) were solely associated with the amnestic MCI subtype, whereas, severe difficulties maintaining sleep (OR = 3.84, 1.13-13.08) were associated with non-amnestic MCI. Our results suggest that poor sleep quality, rather than SDB, is associated with MCI. The selective association of difficulties initiating sleep and early morning awakening with amnestic MCI and of difficulties maintaining sleep with non-amnestic MCI might serve as a marker to improve diagnostic accuracy in the earliest stages of cognitive impairment and will be further investigated in our longitudinal examination.