Association of magnesium intake and vitamin D status with cognitive function in older adults: an analysis of US National Health and Nutrition Examination Survey (NHANES) 2011 to 2014

Purpose: Reduced cognitive function associated with aging has gained increasing attention as the US population ages. Magnesium plays a critical role in vitamin D biosynthesis and metabolism; and deficiencies in magnesium and vitamin D show associations with poor cognition. However, no study has examined their interaction. This study aimed to evaluate the associations of magnesium intake and serum 25-hydroxyvitamin D (25(OH)D) concentrations, indicating vitamin D status, with cognition, and interaction between these nutrients in older adults. Methods: Based on the National Health and Nutrition Survey (NHANES) 2011–2014, the study included 2466 participants aged ≥ 60 years who completed the Digit Symbol Substitution Test (DSST) and had data available on serum 25(OH)D and magnesium intake. Cognitive impairment was defined as a DSST score lower than the lowest quartile. Serum 25(OH)D concentrations were measured by HPLC-tandem mass spectrometry. Results: Higher total magnesium intake was independently associated with higher DSST scores (highest quartile vs lowest: β = 4.34, 95% CI 1.14–7.54). The association of total magnesium intake with high DSST score was primarily observed among women, non-Hispanic whites, physically active participants and those with sufficient vitamin D status, although the interactions were not significant. The odds of cognitive impairment was reduced with increasing intake of total magnesium (p trend < 0.01) and higher level of serum 25(OH)D (p trend = 0.05). Conclusions: Findings suggest that high magnesium intake alone may improve cognitive function in older adults, and the association may be stronger among subjects with sufficient vitamin D status. Further studies are needed to confirm these findings.