Insomnia symptoms, daytime sleepiness, and quality of life in people with Alzheimer’s disease: a secondary cross-sectional analysis

Background Sleep disturbances are common in Alzheimer’s disease (AD), but the relation of insomnia symptoms and daytime sleepiness to patient-reported quality of life (QoL) remains uncertain, particularly in people with substantial cognitive impairment. We examined exploratory associations with four QoL domains. Methods This secondary cross-sectional analysis included 70 participants aged 60–94 years with clinically diagnosed AD recruited from nursing homes and community-based support services in Kraków, Poland. Insomnia symptoms were assessed using the Athens Insomnia Scale (AIS), daytime sleepiness using the Epworth Sleepiness Scale (ESS), and QoL using the World Health Organization Quality of Life–Brief Version (WHOQOL-BREF). Cognitive impairment was assessed using an abbreviated version of the Blessed Dementia Scale (BDS). Associations between sleep measures and the Physical Health, Psychological, Social Relationships, and Environment domains of the WHOQOL-BREF were examined using Spearman correlations and multivariable linear regression. AIS and ESS were entered simultaneously into the regression models, which were adjusted for age, sex, continuous abbreviated BDS score, depressive symptoms, functional status, and care setting. HC3 robust standard errors were used, and the Benjamini–Hochberg false discovery rate (FDR) procedure was applied across eight prespecified sleep–QoL associations. Results Participants were aged 60–94 years, with a mean age of 78.5 ± 7.9 years, and 45.7% were women. The mean AIS score was 9.31 ± 4.01, with 80.0% of participants meeting the AIS threshold for clinically relevant insomnia symptoms. The mean ESS score was 8.91 ± 2.83, and 30.0% had excessive daytime sleepiness. AIS and ESS scores were positively correlated (Spearman’s ρ = 0.622, p < 0.001). In multivariable analyses, greater daytime sleepiness was nominally associated with poorer Physical Health (B = − 1.045, 95% CI − 1.973 to − 0.117; p = 0.027; FDR q = 0.128), whereas greater insomnia symptom severity was nominally associated with poorer Psychological QoL (B = − 0.512, 95% CI − 0.980 to − 0.044; p = 0.032; FDR q = 0.128). Neither association remained statistically significant after FDR correction. No adjusted associations of AIS or ESS with the Social Relationships or Environment domains were observed. The direction of the two principal associations was maintained in expanded and influence sensitivity analyses. Conclusions In this exploratory sample, two adjusted associations were nominally significant, but neither survived correction for eight comparisons. Overlap among questionnaire constructs, uncertainty in self-report with cognitive impairment, and the modest sample size limit interpretation. Larger studies with documented response assistance and complementary sleep assessments are needed. Clinical trial number Not applicable.