Association Between the Creatinine-to-Body Weight Ratio and All-Cause Mortality in a Rural Japanese Community

Background Evidence on the association between the creatinine-to-body weight (Cr/BW) ratio and the risk of all-cause mortality remains limited. In this prospective, population-based cohort study, we examined the association between baseline Cr/BW ratio and survival over 10- and 22-year follow-up periods. Methods Participants included 1553 men (aged 63 ± 14 years) and 1964 women (aged 65 ± 16 years) who participated in the Nomura cohort study conducted in 2002 (first cohort) and 2014 (second cohort) and who continued throughout the follow-up periods (median, 6316 days; interquartile ranges, 3828-8121 days). Participants were categorized into four groups based on the baseline Cr/BW ratio (×100) standard deviation ranges: 0.53-0.96 (Cr/BW ratio-1), 0.97-1.25 (Cr/BW ratio-2), 1.26-1.62 (Cr/BW ratio-3), and 1.63-7.34 (Cr/BW ratio-4). Adjusted relative risk estimates for all-cause mortality were obtained using data from the Basic Resident Register. Cox proportional hazards regression analysis was performed, with the time variable defined as the period between age at recruitment and age at death or censoring. The model included covariates such as age, sex, body height, smoking and alcohol habits, and histories of cardiovascular disease, hypertension, dyslipidemia, diabetes, chronic kidney disease, and hyperuricemia. Results For the 3517 participants, 1196 deaths (34.0%) were documented, including 604 men (38.9% of men) and 592 women (30.1% of women). Analysis of the Cr/BW ratio as a continuous variable revealed a significant positive association with all-cause mortality risk (hazard ratio (HR), 1.73; 95% confidence interval (CI), 1.28-2.35). In multivariate Cox models, the adjusted HRs (95% CI) for mortality relative to the lowest Cr/BW category (ratio-1) were 1.33 (1.07-1.66), 1.36 (1.08-1.70), and 1.59 (1.20-2.11) for ratio-2, ratio-3, and ratio-4, respectively (p for trend = 0.015). Furthermore, considering both sensitivity and specificity, the optimal cutoff value of the Cr/BW ratio for predicting all-cause mortality was determined to be 1.23 (sensitivity, 63.0%; specificity, 56.0%). Conclusion The study demonstrated that the Cr/BW ratio serves as a significant predictor of subsequent mortality risk. Strategies aimed at keeping the Cr/BW ratio within a specific range could contribute to reducing overall mortality.