Neuropsychiatric Inventory-Assessed Nighttime Behavior Accompanies, but Does Not Precede, Progressive Cognitive Decline Independent of Alzheimer's Disease Histopathology

Interrelationship of Sleep Disturbances and Cognitive Status on Mortality

Sleep disturbances may promote the development and advancement of Alzheimer's disease. Our purpose was to determine if sleep disturbances were associated with earlier mortality while accounting for cognition. The National Alzheimer's Coordinating Center database was used to evaluate mortality risk conferred by sleep, and the Montreal Cognitive Assessment score determined cognitive status. Demographics, sleep disturbances, cognitive status, and comorbid/other neuropsychiatric conditions were examined as predictors of survival time via Cox regression. The sample (N = 31,110) had a median age [interquartile range] of 72 [66, 79] years, MoCA score of 23 [16, 26], and survival time of 106.0 months [104.0,108.0]; 10,278 (33%) died during follow-up; 21% (n = 6461) experienced sleep disturbances. Sleep disturbances impacted survival time depending on cognition, with the greatest effect in transition from normal to cognitive impairment (P < .001). Findings support that sleep disturbances negatively impact survival time, and the impact of sleep disturbances on survival time is interrelated with cognition.

Sleep Disturbances Predict Cognitive Decline in Cognitively Healthy Adults

BACKGROUND

The effect of nighttime behaviors on cognition has not been studied independently from other neuropsychiatric symptoms.

OBJECTIVE

We evaluate the following hypotheses that sleep disturbances bring increased risk of earlier cognitive impairment, and more importantly that the effect of sleep disturbances is independent from other neuropsychiatric symptoms that may herald dementia.

METHODS

We used the National Alzheimer's Coordinating Center database to evaluate the relationship between Neuropsychiatric Inventory Questionnaire (NPI-Q) determined nighttime behaviors which served as surrogate for sleep disturbances and cognitive impairment. Montreal Cognitive Assessment scores defined two groups: conversion from 1) normal to mild cognitive impairment (MCI) and 2) MCI to dementia. The effect of nighttime behaviors at initial visit and covariates of age, sex, education, race, and other neuropsychiatric symptoms (NPI-Q), on conversion risk were analyzed using Cox regression.

RESULTS

Nighttime behaviors predicted earlier conversion time from normal cognition to MCI (hazard ratio (HR): 1.09; 95% CI: [1.00, 1.48], p = 0.048) but were not associated with MCI to dementia conversion (HR: 1.01; [0.92, 1.10], p = 0.856). In both groups, older age, female sex, lower education, and neuropsychiatric burden increased conversion risk.

CONCLUSION

Our findings suggest that sleep disturbances predict earlier cognitive decline independently from other neuropsychiatric symptoms that may herald dementia.

Neuropsychiatric Inventory-Questionnaire Assessed Nighttime Behaviors in Cognitively Asymptomatic Patients with Pathologically Confirmed Alzheimer's Disease Predict More Rapid Cognitive Deterioration

BACKGROUND

The temporal relationship between sleep, Alzheimer's disease (AD), and cognitive impairment remains to be further elucidated.

OBJECTIVE

First, we aim to determine whether the Neuropsychiatric Inventory-Questionnaire (NPI-Q) assessed nighttime behaviors prior to cognitive decline influence the rate of cognitive deterioration in pathologically confirmed AD, and second, to assess the possible interactions with APOE allele and cerebral amyloid angiopathy (CAA).

METHODS

The rate of cognitive decline between cognitively asymptomatic participants from the National Alzheimer Coordinating Center who eventually received a neuropathologic diagnosis of AD with (+NTB) or without (-NTB) nighttime behaviors were compared using independent samples t-test. Participants were stratified by APOE carrier and CAA status. Demographic and patient characteristics were assessed using descriptive statistics, and the independent samples t-test was used for continuous variables and chi-square test for categorical variables. The significance level was set at p≤0.05.

RESULTS

The rate of cognitive decline was greater in +NTB (n = 74; 3.30 points/year) than -NTB (n = 330; 2.45 points/year) (p = 0.016), even if there was no difference in cognitive status at onset. This difference was restricted to APOE ɛ4 carriers (p = 0.049) and positive CAA participants (p = 0.020). Significance was not reached in non-carriers (p = 0.186) and negative CAA (p = 0.364). APOE and CAA were not differentially distributed between the NTB groups.

CONCLUSION

NPI-Q assessed nighttime behaviors, a surrogate for sleep disturbances, are associated with more rapidly deteriorating cognition in patients with AD neuropathology who are also carriers of APOE ɛ4 or show CAA.