Background: Sleep disturbance is highly prevalent in dementia syndromes and increasingly viewed as a correlate of disease expression, not just ageing. This study investigated associations between subjective sleep quality, cognitive performance, and structural MRI markers in a dementia syndromes sample, comparing Alzheimer’s disease (AD) and non-AD groups, with exploratory inclusion of objective sleep and nocturnal blood pressure in a sub-sample. Methods: Observational cross-sectional design with 128 memory clinic patients (41 AD, 87 non-AD). Subjective sleep quality assessed via Pittsburgh Sleep Quality Index (PSQI). Cognitive measures: Mini-Mental State Examination (MMSE) for global cognition, Symbol Digit Modalities Test (SDMT) for processing speed, Trail Making Tests (TMT-A/B), and CLOX-1/2 for executive function. MRI markers: Scheltens scale (medial temporal atrophy), Fazekas scale (white matter hyperintensities). An exploratory sub-sample (N = 24) included additional nocturnal and daytime blood pressure monitoring; these data were analyzed descriptively and are reported as hypothesis-generating only. Analyses: group comparisons, Spearman correlations, hierarchical and logistic regression models in the full sample, and descriptive analyses with Spearman correlations in the exploratory sub-sample. Results: The AD group reported poorer sleep quality (higher PSQI) and worse cognitive performance across domains compared with the non-AD group (p < 0.001). Higher PSQI scores were associated with poorer cognitive outcomes, particularly executive function and processing speed, after adjustment for demographics and structural MRI markers (e.g., β = −0.181 to −0.425 for MMSE/SDMT). In the exploratory sub-sample (N = 24), PSQI was correlated with SDMT (ρ = −0.653) and TMT-A (ρ = 0.788). Conclusions: Subjective sleep quality was associated with cognitive performance in individuals with dementia syndromes after accounting for structural MRI markers. These findings suggest that subjective sleep disturbance may represent a complementary clinical dimension warranting further longitudinal research, including evaluation of whether sleep-focused interventions may offer clinical benefits.
Sideri et al. (Wed,) studied this question.