Genetic prediction of serum micronutrient levels and the risk of frailty: Evidence from a Mendelian randomization study

Although observational studies have revealed a link between frailty and serum micronutrient levels, it remains unclear whether these 2 states are directly connected. Thus, Mendelian randomization (MR) was used to investigate the causal relationship between frailty and blood micronutrient levels. Summary-level data for 15 blood micronutrients (copper, selenium, zinc, calcium, iron, magnesium, potassium, folate, carotene, vitamin A, vitamin B6, vitamin B12, vitamin C, vitamin D, and vitamin E) were obtained from people of European ancestry from the Integrative Epidemiology Unit. Single nucleotide polymorphisms associated with the frailty index were extracted from a published meta-analysis study in the UK Biobank and Swedish TwinGene. We used the inverse variance weighted (IVW) method for the primary analysis. We employed pleiotropy residual sum and outlier (MR-PRESSO) tests, MR-Egger intercepts, Cochran Q tests, and leave-one-out analysis to assess causality validity and robustness. Reverse MR analysis was used to determine reverse causation. The IVW results revealed that vitamin D (odds ratio [OR] = 1.096; 95% confidence interval [CI]: 1.019-1.178; P = .014) increased the likelihood of a high risk of frailty, whereas the frailty index had a protective effect on selenium (OR = 0.622; 95% CI: 0.396-0.977; P = .039), carotene (OR = 0.916; 95% CI: 0.858-0.979; P = .009), vitamin C (OR = 0.895; 95% CI: 0.837-0.957; P = .001), iron (OR = 0.921; 95% CI: 0.859-0.988; P = .022), and vitamin E (OR = 0.907; 95% CI: 0.847-0.971; P = .005). The reverse IVW analysis revealed no significant correlation between micronutrient levels and frailty indices. The study revealed causal links between vitamin D and the risk of frailty. Notably, our findings highlight the necessity of adjuvant vitamin D in frailty management.