Relationship between serum calcium and Alzheimer's disease (AD) remains unclear. The aim of this study is to test whether serum calcium is associated with other AD-associated biomarkers and could predict clinical progression in nondemented elders. This was a longitudinal population-based study. The sample was derived from the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort, which included 1224 nondemented elders: 413 cognitively normal (CN) and 811 mild cognition impairment (MCI). Associations were investigated between serum calcium and longitudinal changes in Aβ/tau pathologic features, brain structure, cognitive function, and disease progression. Serum calcium concentrations increased with disease severity. Serum calcium predicted longitudinal cognitive decline and conversion from nondemented status to AD dementia (adjusted HR = 1.41, 95% CI 1.13-1.76). Furthermore, serum calcium levels were negatively correlated with CSF-Aβ42 (β = - 0.558, P = 0.008), FDG-PET (β = - 0.292, P < 0.001), whole brain volume (β = - 0.148, P = 0.001), and middle temporal volume (β = - 0.216, P = 0.042). Similar results were obtained in CN and MCI groups. Higher serum calcium status (even if not hypercalcemia) may increase the risk of AD in elders. Serum calcium is a useful biomarker in predicting clinical progression in nondemented elders. More researches are needed in the future to explore the underlying mechanism.
Keywords: Alzheimer’s disease; Aβ42; Brain volume; Calcium; FDG-PET.