Association between cardiovascular-kidney-metabolic syndrome stages and risk of all-cause mortality in U.S. adults: a cross-sectional survey based on NHANES

Cardiovascular-Kidney-Metabolic (CKM) syndrome became the leading cause of death among U.S. adults in 2021. However, the relationship between different stages of CKM and the risk of all-cause mortality in the U.S. population remains unclear. Data from NHANES 2005–2018 and the Public-use Linked Mortality Files (LMF) were utilized in this study. Kaplan–Meier survival curves were generated to estimate survival probabilities across five CKM stages (stages 0 to 4) and compared using the log-rank test. Hazard ratio (HR) and 95% confidence interval (95%CI) for all-cause mortality were estimated using Cox proportional hazards regression models. Stratified analyses were conducted to explore potential effect modifications by age, sex, education, smoking status, drinking status and the Poverty Income Ratio (PIR). A total of 4,376 all-cause deaths were recorded during a median follow-up period of 7.25 years (IQR: 6.92–7.67). The risk of all-cause mortality increased progressively with higher CKM syndrome stages (P < 0.001). After multivariate adjustment, the risk of all-cause mortality for CKM stages 1 through 4 was 1.05 (95% CI: 0.81–1.44), 1.98 (95% CI: 1.54–2.56), 3.09 (95% CI: 2.36–4.06), and 4.47 (95% CI: 3.47–5.76) times higher than that for CKM stage 0, respectively. Additionally, subgroup analyses revealed that the risk of all-cause mortality in CKM stage 4 was higher among individuals under 60 years of age, females, current smokers, current drinkers, those with less than a high school education, and those with a household poverty index below1.3. Studies have found that populations with more advanced CKM staging have a higher risk of all-cause mortality. These findings underscore the need for targeted public health strategies to reduce mortality risk associated with CKM syndrome.