Baseline Sleep Characteristics and Objective–Subjective Sleep Discordance in Early Alzheimer’s Disease Patients Prior to Lecanemab Therapy

Background and Objective The baseline sleep phenotype of early Alzheimer’s disease (AD) patients entering lecanemab therapy is poorly characterized.Methods Forty-four consecutive early AD patients (mild cognitive impairment or mild dementia) awaiting lecanemab underwent attended polysomnography, the Epworth Sleepiness Scale, Insomnia Severity Index (ISI), Pittsburgh Sleep Quality Index (PSQI), and Beck Depression Inventory (BDI). Forty-four controls without documented cognitive disorder, referred for polysomnography by the study’s sleep specialist over the same period, were balanced on sex, age and apnea–hypopnea index. Comparisons used independent-samples tests with Benjamini–Hochberg false discovery rate correction within pre-specified families.Results Obstructive sleep apnea was prevalent (61.4% moderate-to-severe) despite a body mass index of 22.5 kg/m²; groups were balanced (all p>0.15). Early AD patients showed greater wake after sleep onset (114.0 min vs. 78.7 min; q=0.006), lower sleep efficiency (67.7% vs. 77.2%; q=0.006) and shorter total sleep time (284.0 min vs. 321.1 min; q=0.039) with comparable recording time, and lower REM arousal index (13.9/h vs. 21.3/h; q=0.012). Differences were moderate (|g| 0.49–0.72); sleep-stage distribution and total arousal index did not differ. ISI (3.8 vs. 13.8) and PSQI (4.1 vs. 10.0) were nonetheless lower in AD (both q<0.001; |g| 1.52–1.86); BDI did not differ.Conclusions Early AD patients awaiting lecanemab therapy had a high prevalence of sleep apnea and reduced objective sleep continuity despite reporting fewer subjective sleep complaints than controls, a contrast that may partly reflect the symptomatic sleep-clinic comparator. Objective sleep assessment before initiating lecanemab therapy may therefore be considered.