The present study demonstrated that underweight and low WC prior to PCI were associated with a higher risk of ESRD during a 5.4-year follow-up period after PCI. Moreover, this phenomenon was more obvious in the DM subgroup than in the non-DM group, especially in low WC case. This association persisted after multivariable adjustment for important potential confounders.
Generally, BMI, an internationally accepted standard anthropomorphic measurement, is used to define obesity in research settings . Several studies have examined the association between BMI and the future risk of ESRD. Although the results are conflicting, most epidemiologic studies showed that a higher BMI was associated with an increased risk of kidney disease. Two large epidemiologic studies in the U.S. reported a positive association between BMI and ESRD, and these studies analyzed a broad spectrum of BMI among a large, diverse sample of participants with long-term follow-up for ESRD [11, 12]. It is presumed that a higher BMI is an independent risk factor for ESRD in any ethnic group.
However, the association between BMI with future risk for ESRD tends to be discordant in patients with renal impairment, and this population thus exhibits a so-called “obesity paradox.” Specifically, although a high BMI is associated with all-cause mortality and decreased renal function in patients with earlier stages of CKD, this association is attenuated in patients with advanced CKD [23, 24]. In addition, a few studies also showed that patients with obesity paradoxically exhibited more favorable clinical outcomes with respect to in-hospital, short-, and long-term mortality than those without obesity after PCI [25–28]. Therefore, there are still controversies between BMI and the risk for future ESRD in PCI patients. We therefore considered that longitudinal studies are required to explore the actual relationship between BMI and the risk of ESRD. To the best our knowledge, this is the first nationwide cohort study that examines the relationship between lower BMI and ESRD risk in the Korean population prior to PCI. Our findings were inconsistent with most previous published studies, showing that underweight had the highest risk for ESRD in PCI patients.
Recently, measures of central or abdominal obesity, defined by the WC and waist-hip ratio, have been used as more important predictors to assess the mortality risk than BMI [29, 30]. WC, a representative marker of visceral body fat, was found to correlate with inflammation, whereas subcutaneous body fat may be an indicator of the nutritional status . In patients with ESRD, multiple studies identified WC as a direct and strong predictor of mortality and incident cardiovascular events, even after adjusting for the BMI and other risk factors [32, 33]. In fact, many studies have shown that central obesity or abdominal adiposity measured by the WC was linearly associated with a higher risk of mortality after PCI . However, our findings show that a WC under ~ 85/~80 cm showed the highest risk for future ESRD development. Increasing WC was also linearly associated with a lower risk of future ESRD development. However, unlike BMI, low WC prior to PCI was a risk for ESRD in the only DM group, suggesting that suggest that WC maybe more accurate than BMI to estimate the risk for ESRD in prior to PCI. Central obesity could be a risk factor for ESRD development in all the total, DM and non-DM groups, as well as the low WC group in our study.
The exact mechanisms by which a low WC presents a high risk for ESRD development in PCI patients are not known. High adiposity itself has been reported as a predictor of good prognosis among patients with coronary artery disease. Lavie et al. reported that a high percentage of body fat, which was measured using the sum of the skinfold method, was associated with a low mortality rate among patients with stable angina .
There are some limitation in this study. First, we did not collect relevant information on the food habits or other comorbidities that might affect weight. Second, this study did not consider use of medications such as hypoglycemic agents or lipid lowing agents, and adherence to treatment. Third, we were unable to obtain more information about the causes of ESRD. Fourth, we used data from the NHIS checkup program in a Korean population; therefore, we cannot generalize the results to other ethnic groups. Fifth, although we monitored the subjects for 5.4 years, the time of follow-up is short for patients to develop ESRD.