Chronic kidney disease among adult participants of the ELSA-Brasil cohort: association with race and socioeconomic position Sandhi M Barreto, 1 Roberto M Ladeira, 1,2 Bruce B Duncan, 3 Maria Ines Schmidt, 3 Antonio A Lopes, 4 Isabela M Benseñor, 5 Dora Chor, 6 Rosane H Griep, 7 Pedro G Vidigal, 1 Antonio P Ribeiro, 1 Paulo A Lotufo, 5 José Geraldo Mill 8 1 Medical School & Hospital das Clínicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil 2 Department of Health, Belo Horizonte, Brazil 3 Medical School, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil 4 Department of Internal Medicine, Universidade Federal da Bahia, Salvador, Brazil 5 Center for Clinical and Epidemiologic Research, Universidade de São Paulo, São Paulo, Brazil 6 National School of Public Health, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil 7 Laboratory of Health and Environment Education, Fundação Oswaldo Cruz, Brazil 8 Department of Physiological Sciences, Universidade Federal do Espírito Santo, Brazil Correspondence to Professor Sandhi M Barreto, Faculdade de Medicina, Universidade Federal de Minas Gerais, Av. Alfredo Balena 190, Belo Horizonte CEP 30320050 Brazil; sbarreto@medicina.ufmg.br Received 26 March 2015 Revised 31 August 2015 Accepted 4 October 2015 To cite: Barreto SM, Ladeira RM, Duncan BB, et al. J Epidemiol Community Health Published Online First: [ please include Day Month Year] doi:10.1136/jech-2015- 205834 ABSTRACT Background There is increased interest in understanding why chronic kidney disease (CKD) rates vary across races and socioeconomic groups. We investigated the distribution of estimated glomerular filtration rate (eGFR), urinary albumin–creatinine ratio (ACR) and CKD according to these factors in Brazilian adults. Methods Using baseline data (2008–2010) of 14 636 public sector employees (35–74 years) enrolled in the Brazilian Longitudinal Study of Adult Health (ELSA)-Brasil multicentre cohort, we estimated the prevalence of CKD by sex, age, race and socioeconomic factors. CKD was defined as ACR≥30 mg/g and/or eGFR<60 mL/min/ 1.73 m 2 . GFR was estimated by CKD epidemiology collaboration without correction for race. We used logistic regression to estimate the association of race and socioeconomic position (education, income, social class and occupational nature) with CKD after adjusting for sex, age and several health-related factors. Results The prevalence of high ACR or low eGFR, in isolation and combined, increased with age, and was higher in individuals with lower socioeconomic position and among black individuals and indigenous individuals. The overall prevalence of CKD was 8.9%. After full adjustments, it was similar in men and women (OR=0.90; 95% CI 0.79 to 1.02) and increased with age (OR=1.07; 95% CI 1.06 to 1.08). Compared to white individuals, black individuals (OR=1.23; 95% CI 1.03 to 1.47), ‘pardos’ (OR=1.16; 95% CI 1.00 to 1.35) and Indigenous (OR=1.72; 95% CI 1.07 to 2.76) people had higher odds for CKD. Having high school (OR=1.15; 95% CI 1.00 to 1.34) or elementary education (OR=1.23; 95% CI 1.03 to 1.47) increased the odds for CKD compared to those having a university degree. Conclusions There were marked discrepancies in the increases in reduced eGFR and high ACR with age and race. The higher prevalences of CKD in individuals with lower educational status and in non-whites were not explained by differences in health-related factors. INTRODUCTION Chronic kidney disease (CKD) is one of the major public health problems of the 21st century due to its high morbidity and associated mortality, elevated social and individual costs and increasing prevalence in most countries. 1–5 It is a complex and progressive disease defined by persistent kidney damage, gener- ally marked by urinary albumin–creatinine ratio (ACR) equal or superior to 30 mg/g, or a glomerular filtration rate (GFR) lower than 60 mL/min/ 1.73 m 2 . 6 CKD affects 10–16% of the adults living in Asia, Europe, Australia and the USA, 7–10 but data on the incidence and prevalence of CKD, considering its full spectrum, in the general population of Latin America, including Brazil, are very sparse. 11 Most of the available data on the incidence and preva- lence of CKD refer to estimates of people under renal replacement therapy (RRT), that is, mainten- ance dialysis or kidney transplants, and these figures show steady increases in recent years. 12–14 According to a review study, 1.9 million patients are undergoing RRTworldwide, with an annual ini- tiation rate at 73 per million population (pmp). 15 Existing data indicate that the prevalence of patients under RRT in Latin America increased from 119 patients pmp in 1991 to 568 pmp in 2008, with a wide variation between countries. 16 In Brazil, CKD is estimated to cause 4500–6000 deaths/year. 17 Between 2000 and 2012, the number of patients with CKD receiving publicly financed maintenance dialysis increased by 3.6% per year, reaching a total number of 104 433 in 2012. 18 In 2011, 31.2% of the patients under RRT were on the waiting list for renal transplant. 19 However, there is no information regarding the prevalence of early stages of CKD in Brazilian adults. Owing to the difficulty in direct measurement, the GFR is estimated by equations that take into consideration the serum creatinine, sex, age and a correction factor for black individuals because the concentration of serum creatinine is affected by muscle mass, which is generally greater in African-Americans. 20 The most widely used equa- tions estimated glomerular filtration rate (eGFR) are the modified diet in renal disease (MDRD) and the CKD epidemiology collaboration (CKD-EPI). 21 22 However, there is evidence that the CKD-EPI equation is better for estimating GFR and for predicting prognosis, 23 24 though the CKD-EPI proposing study developed in the USA included a limited number of elders and people of racial and ethnic minorities. 22 In Brazil, two studies validated the CKD-EPI equation. One used the plasma clearance of Iohexol 25 as a gold standard and the other 51Cr-EDTA. 26 The first study showed that CKD-EPI was better than MDRD at detecting a Barreto SM, et al. J Epidemiol Community Health 2015;0:1–10. doi:10.1136/jech-2015-205834 1 Research report JECH Online First, published on October 28, 2015 as 10.1136/jech-2015-205834 Copyright Article author (or their employer) 2015. Produced by BMJ Publishing Group Ltd under licence.