Analysis of Correlation between Age and Satisfied Total Weight Loss Percentage Outcome at 1 Year after Bariatric Surgery using the Restricted Cubic Spline Function: A Retrospective Study in China

Objective This study aims to explore the relationship between age and whether the percentage of total weight loss (TWL%) is ≥ 25% or not at 1 year after bariatric surgery (BS). We aimed to provide evidence for the stratified treatment of spatients with obesity at different ages. Methods The primary outcome evaluated was whether TWL% was no less than 25% at 1 year after BS. A TWL% ≥ 25% was defined as a satisfied TWL% outcome. Logistic regression analysis and the restricted cubic spline (RCS) function were used to analyze the relationship between age and the satisfied TWL% outcome at 1 year after BS. Results Two hundred and ninety-one patients were included in our study. After adjusting for potential confounders, the odds ratios (ORs) of the corresponding quartiles of age associated with satisfied TWL% outcome were 1.00 (reference), 1.117 [95% confidence interval (95% CI) = 0.540–2.311], 1.378 (95% CI = 0.647–2.935), and 0.406 (95% CI = 0.184–0.895). RCS analysis revealed a non-linear inverted L-shaped association between age and satisfied TWL% outcome at 1 year after BS (non-linear P = 0.033). Conclusion Age was an independent predictor of satisfied TWL% outcome one year following BS, and our study considered 32 years as a potential cut-off point. For Chinese patients over the age of 32 who are eligible for BS, it may be beneficial to do BS earlier as the probability of achieving a satisfied TWL% outcome may decrease with age. Graphical Abstract