Association of body mass index with kidney function and mortality in high cardiovascular risk population: A nationwide prospective cohort study.

Background: There is increasing awareness of the impact of obesity and underweight on cardiovascular (CV) disease, chronic kidney disease (CKD) and mortality. Abnormal body mass index (BMI) might be associated with worse clinical outcomes, including CKD progression, but limited evidence exists among Asian patients with high CV risk.

Objective: To investigate the association of BMI with progressive loss of kidney function and all-cause mortality in Thai patients with high CV risk.

Methods: In a national cohort of 5887 high CV risk subjects, we assessed the association of high BMI with the composite renal outcome (estimated glomerular filtration rate [eGFR] decline over 40%, eGFR less than 15 mL/min/1.73 m² , doubling of serum creatinine, initiation of dialysis and death related to renal causes) and with all-cause mortality in Cox proportional hazards models.

Results: A total of 5887 participants (3217 male and 2670 female) with high CV risk were enrolled. Participants were classified into five groups by their baseline BMI; <20 kg/m² (n = 482), 20-24.9 kg/m² (n = 2437), 25-29.9 kg/m² (n = 2140), 30-34.9 kg/m² (n = 665) and 35 kg/m² (n = 163), respectively. On multivariate analysis of Cox proportional hazards models, adjusted for other covariates, baseline BMI ≥35 kg/m² was an independent predictor of loss of kidney function (HR 1.60, 95% CI 1.04-2.40) and all-cause mortality (HR 2.68, 95% CI 1.50-4.80). Baseline BMI <20 kg/m² was an independent predictor of all-cause mortality as well (adjusted HR 2.26, 95% CI 1.50-3.42).

Conclusion: In the high CV risk Thai population, a BMI of 35 kg/m² or more is associated with loss of kidney function and mortality. On the other hand, a BMI less than 20 kg/m² is also associated with all-cause mortality.