Association of remnant cholesterol with frailty: findings from observational and Mendelian randomization analyses

BACKGROUND: Recent insights suggest that remnant cholesterol (RC) plays a role in cellular senescence, yet its specific contribution to frailty remains indeterminate. Through the integration of observational and mendelian randomization (MR) studies, this research explores the impact of elevated serum RC levels on frailty susceptibility. METHODS: A dual-method approach, combining an observational study with an MR study, was employed to investigate the connection between RC and frailty. The observational study included 11,838 participants from the National Health and Nutrition Examination Survey. Multivariable logistic regression and propensity score matching were employed to control for potential confounders. The non-linear relationship was assessed using restricted cubic splines. To circumvent observational study limitations, a two-sample MR analysis was conducted using the inverse-variance weighted method, leveraging genome-wide association studies (GWAS) data. RESULTS: After adjusting for potential confounding variables, the observational study identified a significant association between high serum RC levels and frailty in middle-aged and older adults (odds ratio [OR] = 1.67, 95% confidence interval [CI] = 1.20 to 2.33, P = 0.003), exhibiting a non-linear dose–response correlation (non-linear P = 0.011). This association persisted after propensity score matching (OR = 1.53, 95% CI = 1.14 to 2.06, P = 0.005). The MR study echoed these results, demonstrating a causal association of RC with the frailty index (β = 0.059, 95% CI = 0.033 to 0.085, P = 1.05E-05), consistent with the observational findings (β = 0.017, 95% CI = 0.008 to 0.026, P = 4.51E-04). CONCLUSION: This study provides evidence that higher RC levels amplify frailty risk in middle-aged and older adults, implying that the reduction of RC levels may present a promising strategy for frailty prevention and management. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12944-023-01882-4.