Daytime Sleepiness, Apnea, Neuroimaging Correlates and Cortisol Dysregulation in a Memory Clinic Cohort.

Background: Sleep disturbances as well as cortisol hypersecretion are increasingly acknowledged as risk factors for Alzheimer's disease (AD). However, the mechanisms underlying the association, and the interplay with cortisol abnormalities, remain unclear.

Objectives: This study aims to identify how self-reported sleep disturbances are associated with structural brain measures and diurnal cortisol dysregulation among memory clinic patients.

Design: A cross-sectional study performed at Karolinska University Hospital Memory Clinic, Sweden.

Participants: The study was based on 146 memory clinic patients diagnosed with either subjective cognitive impairment or mild cognitive impairment.

Measurements: Self-reported sleep was measured using the Karolinska Sleep Questionnaire. MRI or CT was used to quantify structural brain measures using four visual rating scales (Scheltens, Pasquier, Koedam, and Fazekas scales), and salivary cortisol was sampled to measure diurnal cortisol patterns through measures of cortisol immediately after awakening, cortisol awakening response, bedtime cortisol, total cortisol from awakening to bedtime, and the AM/PM cortisol ratio.

Results: Increased sleep apnea index (OR=1.20, 95% CI=1.04:1.39, p=0.015) was associated with greater odds of posterior brain atrophy, measured by the Koedam visual rating scale, and reduced awakening cortisol (β=-0.03, 95% CI=-0.07:0.00, p=0.045). Increased daytime sleepiness was associated with both reduced awakening cortisol (β=-0.03, 95% CI=-0.06:0.00, p=0.025) and a reduced AM/PM cortisol ratio (β=-0.04, CI=-0.08:-0.01, p= 0.021).

Conclusion: In a memory clinic cohort self-reported sleep disturbances are associated with both worse structural brain tissue integrity and altered diurnal cortisol profiles. These findings may add insights into possible mechanisms behind sleep disturbances in aging with subjective and cognitive impairment.