The metabolic syndrome is a risk factor for the development of diabetes and cardiovascular disease; however, no prospective studies have examined the metabolic syndrome as a risk factor for chronic kidney disease (CKD). A total of 10,096 nondiabetic participants who were in the Atherosclerosis Risk in Communities study and had normal baseline kidney function composed the study cohort. The metabolic syndrome was defined according to recent guidelines from the National Cholesterol Education Program. Incident CKD was defined as an estimated GFR (eGFR) <60 ml/min per 1.73 m 2 at study year 9 among those with an eGFR >60 ml/min per 1.73 m 2 at baseline. T he metabolic syndrome, also known as the insulin resistance syndrome, is characterized by abdominal obesity, dyslipidemia, hypertension, and hyperglycemia and is present in approximately 20% of US adults (1). Individuals with the metabolic syndrome are at increased risk for diabetes and cardiovascular disease (2), as well as cardiovascular and all-cause mortality (3,4). The prevalence of chronic kidney disease (CKD) is also rising, affecting approximately 8 million adults in the United States (5). Cross-sectional studies have demonstrated a link between the metabolic syndrome and CKD (6,7). However, whether the metabolic syndrome contributes to the development of CKD is unknown.Diabetes is a major risk factor for the initiation and progression of CKD (8,9), and individuals with evidence of the metabolic syndrome have a substantial risk for developing type 2 diabetes over time (2). Epidemiologic studies have linked the metabolic syndrome with an increased risk for microalbuminuria, an early marker of kidney injury (7,10 -13); few studies have evaluated the relation between the metabolic syndrome and CKD (6,7). These studies have been limited by cross-sectional design, the inclusion of subjects with diabetes, and the use of proxies of insulin resistance, rather than recently proposed clinical criteria defining the metabolic syndrome (14). To date, no prospective longitudinal studies have examined the risk for CKD among individuals with the metabolic syndrome. It remains unclear whether the syndrome is a cause or a consequence of reduced kidney function and whether the associations are independent of diabetes.To determine whether the metabolic syndrome was associated with the development of CKD, we examined data from a large, community-based, prospective cohort of adults. We hypothesized that among individuals with normal or near-normal kidney function at baseline, the metabolic syndrome would be associated with the development of CKD over time. Moreover, we hypothesized that this association would be independent of diabetes and hypertension, the leading causes of CKD in the United States.
Materials and Methods
Study PopulationThe Atherosclerosis Risk in Communities (ARIC) Study is a prospective longitudinal study of cardiovascular disease risk factors (15). The ARIC cohort consists of Ͼ15,000 black and white individuals aged 45 to 64 at study entry, sampled at random ...