Abstract
INTRODUCTION: Alzheimer's disease (AD) blood biomarkers hold clinical potential but their concentration may vary with somatic conditions. METHODS: We investigated the concentration of six AD blood biomarkers in relation to multimorbidity as disease count and four multimorbidity patterns in 2290 cognitively unimpaired older adults. RESULTS: Levels of phosphorylated tau (p-tau)181, p-tau217, neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP) increased with increasing number of diseases. In multi-adjusted regressions, compared to individuals without multimorbidity, the anemia/sensory impairment pattern was associated with altered levels of all biomarkers except amyloid beta (Aβ)42/40, GFAP, and total tau (p-tau181: β = 0.18, 95% confidence interval [CI]: 0.08, 0.28; p-tau217: β = 0.11, 95% CI: 0.03, 0.18; NfL: β = 0.14, 95% CI: 0.06, 0.21) and the cardiometabolic/inflammatory pattern was associated with altered levels of all biomarkers except Aβ42/40 and GFAP (p-tau181: β = 0.24, 95% CI: 0.12, 0.36; p-tau217: β = 0.23, 95% CI: 0.14, 0.32; NfL: β = 0.32, 95% CI: 0.23, 0.40; total tau: β = 0.23, 95% CI: 0.07, 0.39). Results remained unchanged after excluding those who developed dementia in 15 years. DISCUSSION: More diseases and specific multimorbidity patterns altered the levels of several AD blood biomarkers, highlighting caution when using them in adults with complex health profiles. HIGHLIGHTS: In cognitively unimpaired older adults blood biomarkers of Alzheimer's disease varied depending on the number of chronic diseases and specific patterns of multimorbidity. Phosphorylated tau (p-tau)181, p-tau217, neurofilament light chain (NfL), and glial fibrillary acidic protein levels increased along with increasing numbers of chronic diseases. P-tau181, p-tau217, and NfL levels were significantly higher in individuals in the anemia/sensory impairment and cardiometabolic/inflammatory multimorbidity patterns compared to those without multimorbidity. Results remained unchanged after excluding participants who developed dementia during 15-year follow-up.