title: Association between social adaptability index and survival of patients with chronic kidney disease.
abstract: BACKGROUND
  While individual socioeconomic factors have been associated with clinical outcome, a composite index has not been developed. In this project, we tested the hypothesis that Social Adaptability Index (SAI) based on employment, education, income, marital status and substance abuse is associated with survival in chronic kidney disease (CKD) patients.
  
  
  METHODS
  This is a retrospective cohort study of patients with CKD stage 2 or greater. We used the Third National Health and Nutrition Examination Survey (NHANES III) cohort data between 1988 and 1994 including those 18 years or older. Our primary variable of interest is SAI. Each component of SAI (employment status, education, marital status, and substance abuse) has been graded on the scale of 0-3, income has been graded on the scale 0-1. Age, sex, race, diabetes, co-morbidity index, body mass index (BMI), geographic location, haemoglobin, serum creatinine, serum albumin, serum cholesterol and Hba1c were used as covariates in multivariate analysis. The outcome of the study is patient's mortality. The time to death was calculated as time between the first interview by NHANES and death.
  
  
  RESULTS
  We analysed 13 400 subjects with mean age of 50.6 ± 20-53.6% males, 44.4% white, 29.7% African American and 22.1% Mexican American-with 8.5% having diabetes, with an average number of co-morbid conditions of 2.7 ± 1.1. Lower SAI is associated with greater stage of CKD. Higher SAI was associated with decreased mortality [hazard ratio (HR) 0.88, P < 0.001, 95% confidence interval (CI) 0.86-0.89]. When SAI quintiles were analysed, we demonstrated a 'dose-dependent' association between SAI and survival. Subgroup analysis showed that this association of SAI and survival was present in all studied subgroups. The limitations of the study include retrospective design, potential misreporting and misclassification, and reverse causality.
  
  
  CONCLUSIONS
  We demonstrated that SAI has a strong and clinically significant association with mortality in CKD patients.
authors.affiliation: Division of Nephrology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA. agoldfar@bidmc.harvard.edu
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Goldfarb-Rumyantzev
authors.forename: Preeti
authors.initials: P
authors.lastname: Rout
authors.forename: Gurprataap S
authors.initials: GS
authors.lastname: Sandhu
authors.forename: Muhammad
authors.initials: M
authors.lastname: Khattak
authors.forename: Hongying
authors.initials: H
authors.lastname: Tang
authors.forename: Anna
authors.initials: A
authors.lastname: Barenbaum
mesh_terms: D000328:Adult; D000368:Aged; D002908:Chronic Disease; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000401:mortality* / Q000523:psychology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012917:Social Adjustment; D012959:Socioeconomic Factors