Associations of serum magnesium and magnesium intake with brain morphology and cognitive function in Puerto Rican adults.

BACKGROUND: Magnesium's (Mg) role in brain aging is under-studied. We examined associations of dietary and serum Mg with MRI and cognitive measures in a cohort with >10 y follow-up. METHODS: Adults from the Boston Puerto Rican Health Study who underwent MRI (n = 218 with serum Mg, n = 198 with Mg intake) and cognitive testing (n = 1049 with serum Mg, n = 1363 with Mg intake) were included. Hypomagnesemia was defined as serum Mg <0.75 mmol/L, and adequate Mg intake as ≥ the Estimated Average Requirement (males: 350 mg/d, females: 265 mg/d). Multivariable linear regression and linear mixed-effects models were used to estimate associations of Mg with brain age gap (z-score), volumes (% of total intracranial volume), and cognitive scores (z-score). Effect modification by diabetes, hypertension, dyslipidemia, calcium: Mg intake ratio, or ApoE4 was evaluated. RESULTS: In the full sample, hypomagnesemia was not associated with brain MRI measures, but with global cognitive function [β (95% CI) = -0.058 (-0.11, -0.0020)], in fully adjusted models. Adequate Mg intake was associated with volumes of total gray matter [β (95% CI) = 2.83 (0.56, 5.11)], white matter [β (95% CI) = 1.54 (0.22, 2.86)], and multiple subregions, but not cognition. In participants with diabetes, hypomagnesemia was associated with lower volumes of multiple brain regions, which were not observed in participants without diabetes (pinteraction < .05). Limited or no interaction was detected for other potential modifiers, despite some variation in association direction or magnitude across subgroups. CONCLUSIONS: Diabetes modified Mg's association with brain volumes. Mg merits more attention among people with diabetes for preventing neurodegeneration.