The association between the metabolic score for insulin resistance (METS-IR) index and urinary incontinence in the United States: results from the National Health and Nutrition Examination Survey (NHANES) 2001-2018

Background The association between insulin resistance and urinary incontinence (UI) has not been investigated widely. The purpose of this study is to assess the relationship between a novel indicator for assessing insulin resistance the metabolic score for insulin resistance (METS-IR) index and urinary incontinence (UI).Methods This study utilized data from National Health and Nutrition Examination Survey (NHANES) 2001-2018. Weighted multivariable logistic regression models were conducted to explore the association of METS-IR index with three types of UI [stress UI (SUI), urgency UI (UUI), and mixed UI (MUI)]. Smooth curve fitting was utilized to investigate the linear relationship. Subgroup analysis was used to examine the stability of the connection between METS-IR index and UI in different stratifications.Results A total of 17,474 participants were included in this study, of whom 23.76% had SUI, 20.05% had UUI, and 9.59% had MUI. METS-IR index was positively associated with three types of UI with full adjustment [SUI: odds ratio (OR) = 1.023, 95% confidence interval (CI) 1.019-1.027; UUI: OR = 1.015, 95% CI 1.011-1.019; MUI: OR = 1.020, 95% CI 1.016-1.025, all p < 0.001]. After transferring METS-IR index into a categorical variable by quartiles, the positive connection between METS-IR index and UI was still observed in the highest METS-IR group compared to the lowest METS-IR interval (SUI: OR = 2.266, 95% CI 1.947-2.637, p < 0.001; UUI: OR = 1.534, 95% CI 1.344-1.750, p < 0.001; MUI: OR = 2.044, 95% CI 1.707-2.448, p < 0.001). The analysis of smooth curves fitting showed that METS-IR index was positively linearly related to three types of UI. Moreover, the association between METS-IR index and SUI was more significant in females compared to males (p for interaction < 0.05).Conclusion An elevated METS-IR index was related to increased risks of three types of UI (SUI, UUI, and MUI) in the United States population. METS-IR index was more significantly connected to SUI in females than males. The association between insulin resistance and UI needs to be explored with more studies.