Mediation of the association between sedentary behavior and complex multimorbidity by the hs-CRP/HDL-C ratio

This study aimed to investigate the association between sedentary behavior and complex multimorbidity among American adults, verify the mediating role of the high-sensitivity C-reactive protein/high-density lipoprotein cholesterol (hs-CRP/HDL-C) ratio in this relationship, and provide a theoretical basis for the prevention and control of chronic diseases. A total of 8246 adults aged ≥20 years from the National Health and Nutrition Examination Survey 2015 to 2020 were enrolled as study participants. Sedentary time was collected via questionnaire surveys, while hs-CRP and HDL-C levels were obtained through laboratory tests. Complex multimorbidity (defined as the coexistence of ≥3 chronic diseases) was determined based on clinical diagnoses. Logistic regression analysis was used to examine the association between sedentary behavior and complex multimorbidity. A mediation effect model was applied to quantify the mediating effect of the hs-CRP/HDL-C ratio, and subgroup analyses were conducted to explore population heterogeneity. The prevalence of complex multimorbidity in the study population was 25.72%, with a mean daily sedentary time of 5.87 hours. After adjusting for potential confounding factors, each 1-hour increase in daily sedentary time was associated with a 3.46% higher risk of complex multimorbidity (odds ratio = 1.03, 95% confidence interval: 1.02-1.05, P < .001). Restricted cubic spline analysis revealed a linear association between sedentary time and complex multimorbidity. Mediation effect analysis indicated that the hs-CRP/HDL-C ratio exerted a partial mediating effect on the association, accounting for 5.17% of the total effect (95% confidence interval: 0.0001-0.0004, P < .001). Subgroup analyses demonstrated that this mediating effect was more pronounced in individuals aged 45 to 64 years and in males, with mediating proportions of 2.67% and 5.86%, respectively (both P < .05). Sedentary behavior may be positively associated with the risk of complex multimorbidity among American adults, and the hs-CRP/HDL-C ratio partially explain this association.