Comorbidities and health‐care use prior to early‐onset Alzheimer's disease: A population‐based case–control study

Abstract INTRODUCTION We examined whether comorbidities and health‐care use differ between individuals later diagnosed with early‐onset Alzheimer's disease (EOAD) and matched controls during the 15 years preceding diagnosis. METHODS This population‐based case–control study included 407 EOAD patients diagnosed at two Finnish university hospitals (2010–2021), and 4035 age‐ and sex‐matched controls. Prior diagnoses and health‐care visits were obtained from nationwide registers. RESULTS EOAD patients had higher prevalence of vertigo (5.9% vs. 2.1%, p < 0.001), depression (5.7% vs. 2.3%, p < 0.001), headache (4.9% vs. 1.6%, p < 0.001), delirium (1.5% vs. 0.1%, p < 0.001), brain injuries (2.9% vs. 0.9%, p = 0.002), thyroid disorders (2.5% vs. 0.8%, p = 0.008), alcohol‐related disorders (3.4% vs. 1.4%, p = 0.009), epilepsy (2.2% vs. 0.7%, p = 0.009), strokes (4.4% vs. 2.0%, p = 0.008), and otorhinolaryngologic diseases (5.2% vs. 2.9%, p = 0.027) 1–5 years before diagnosis. Only otorhinolaryngologic diseases (4.7% vs. 2.1%, p = 0.036) differed 6 to 10 years prior, whereas no differences were seen 11 to 15 years before diagnosis. Hypertension and dyslipidemia showed no between‐group differences. Health‐care use increased markedly from year before EOAD diagnosis. DISCUSSION EOAD is preceded by recognizable patterns of morbidity and increased health‐care use, which may support earlier detection.