Dietary Magnesium and Incident Frailty in Older People at Risk for Knee Osteoarthritis: An Eight-Year Longitudinal Study

Inadequate magnesium (Mg) intake is associated with lower physical performance, but the relationship with frailty in older people is unclear. Therefore, we aimed to investigate whether higher dietary Mg intake is associated with a lower risk of frailty in a large cohort of North American individuals. Details regarding Mg intake were recorded through a food-frequency questionnaire (FFQ) and categorized as greater than/equal to Recommended Dietary Allowance (RDA) vs. lower. Frailty was defined using the Study of Osteoporotic Fractures index. Multivariable Cox’s regression analyses, calculating hazard ratios (HRs) with 95% confidence intervals (CIs), were undertaken by sex. In total, 4421 individuals with knee osteoarthritis or who were at high risk without frailty at baseline (mean age: 61.3, females = 58.0%) were followed for 8 years. After adjusting for 11 potential baseline confounders, reaching the RDA for Mg lowered risk of frailty among men (total n = 1857, HR = 0.51; 95% CI: 0.26–0.93), whilst no significant associations were found in women (total n = 2564). Each 100 mg of dietary Mg intake at baseline corresponded to a 22% reduction in men (HR = 0.78; 95% CI: 0.62–0.97; p = 0.03), but not in women (HR = 1.05; 95% CI: 0.89–1.23). In conclusion, higher dietary Mg intake appears to reduce the risk of frailty in men, but not in women.