High muscle-to-fat ratio is associated with lower risk of chronic kidney disease development

Abstract

Background: Obesity, a known risk factor for chronic kidney disease (CKD), is generally assessed using body mass index (BMI). However, BMI may not effectively reflect body composition, and the impact of muscle-to-fat (MF) mass balance on kidney function has not been elucidated. This study evaluated the association between body muscle and fat mass balance, represented as the MF ratio, and incident CKD development.

Methods: Data were retrieved from a prospective community-based cohort study (Korean Genome and Epidemiology Study). Muscle and fat mass were measured using multifrequency bioelectrical impedance analysis. The study endpoint was incident CKD (estimated glomerular filtration rate <60 mL/min/1.73 m² in at least two or more consecutive measurements during the follow-up period).

Results: Totally, 7682 participants were evaluated. Their mean age was 51.7 ± 8.7 years, and 48% of the subjects were men. During a median follow-up of 140.0 (70.0-143.0) months, 633 (8.2%) subjects developed incident CKD. When the association between body composition and incident CKD was investigated, multivariable Cox proportional hazard analysis revealed that increase in MF ratio was related with a decreased risk of CKD development [per 1 increase in MF ratio: hazard ratio (HR), 0.86; 95% confidence interval (CI), 0.77-0.96; P = 0.008]. This association was also maintained when MF ratio was dichotomized according to sex-specific median values (high vs. low: HR, 0.83; 95% CI, 0.70-0.98; P = 0.031). Analyses preformed in a propensity score matched group also revealed a similar decreased risk of incident CKD in high MF ratio participants (high vs. low: HR, 0.84; 95% CI, 0.71-0.98; P = 0.037). This relationship between MF ratio and incident CKD risk was consistently significant across subgroups stratified by age, sex, hypertension, estimated glomerular filtration rate categories, and proteinuria. Among different BMI groups (normal, overweight, and obese), the relationship between high MF ratio and lower incident CKD risk was significant only in overweight and obese subjects.

Conclusions: Lower fat mass relative to muscle mass may lower the risk of CKD development in individuals with normal renal function. This relationship seems more prominent in overweight and obese subjects than in normal weight subjects.

Keywords: Body mass index; Chronic kidney disease; Fat mass; Muscle mass; Muscle-to-fat ratio; Obesity.

Figure 1

Comparison of risk for CKD development according to combination of BMI and sex‐specific median values of the MF ratio (low BMI with high MF ratio as reference group). BMI, body mass index; CI, confidence interval; CKD, chronic kidney disease; HRs, hazard ratios; MF ratio, muscle‐to‐fat ratio. ^†World Health Organization obesity classification for Asian population was used: normal (BMI <23.0 kg/m²), overweight (BMI 23.0–27.4 kg/m²), and obese (BMI ≥27.5 kg/m²).

Figure 2

The prevalence of CKD according to sex‐specific median of the MF ratio in different BMI groups (P for trend <0.001). BMI, body mass index; CKD, chronic kidney disease; MF ratio, muscle‐to‐fat ratio. ^*World Health Organization obesity classification for Asian population was used: normal (BMI <23.0 kg/m²), overweight (BMI 23.0–27.4 kg/m²), and obese (BMI ≥27.5 kg/m²).