Multimorbidity and neuroimaging biomarkers among cognitively normal persons

Objective: To assess the cross-sectional association between multimorbidity and imaging biomarkers of brain pathology in the population-based Mayo Clinic Study of Aging (MCSA). Methods: The study consisted of 1,449 MCSA participants who were cognitively normal at the time of MRI. A subset of the participants also had 11C-Pittsburgh compound B (n 5 689) and 18fluorodeoxyglucose (n 5 688) PET scans available. Information on multimorbidity (defined as 2 chronic conditions) in the 5 years prior to the first imaging study was captured from the medical record using ICD-9 codes for chronic conditions and the Rochester Epidemiology Project medical records linkage system. The cross-sectional association of multimorbidity and imaging biomarkers was examined using logistic and linear regression models. Results: Among 1,449 cognitively normal participants (mean age 79 years; 50.9% men), 85.4% had multimorbidity (2 chronic conditions). Multimorbidity and severe multimorbidity (4 chronic conditions) were associated with abnormal Alzheimer disease (AD) signature meta-region of interest (meta-ROI) 18F-FDG hypometabolism (odds ratio [OR] 2.03; 95% confidence interval [CI] 1.10-3.77 and OR 2.22; 95% CI 1.18-4.16, respectively), and with abnormal AD signature MRI cortical thickness (OR 1.53; 95% CI 1.09-2.16 and OR 1.76; 95% CI 1.24-2.51, respectively), but was not associated with amyloid accumulation. Conclusions: Multimorbidity was associated with brain pathology through mechanisms independent of amyloid deposition and such neuronal injury and pathology was present before any symptomatic evidence of cognitive impairment. Longitudinal follow-up will provide insights into potential causal associations of multimorbidity with changes in brain pathology.