Social Adaptability Index: application and outcomes in a dialysis population

Background. Patient groups associated with disparities in health care are usually defined on the basis of race, gender or geographic location. Social Adaptability Index (SAI), calculated based on education, marital status, income, employment and substance abuse, has been strongly associated with clinical outcome in other patient populations and may be used to identify individuals at risk. We used data from the United States Renal Data System to evaluate the role of SAI in survival of patients on dialysis. Methods. We used Cox model analyses to study the association between SAI and patient survival in patients with ESRD on dialysis, as well as in the subgroups based on age, race, sex, comorbidites and diabetic status. Results. We analyzed 3396 patients (age of ESRD onset 56.9 +/- 16.1 years, 54.2% males, 64.2% white, 30.3% African-American). Mean SAI of the entire population was 7.1 +/- 2.5 (range 0-12 points). SAI was higher in whites (7.4 +/- 2.4) than in African-Americans (6.5 +/- 2.5) (analysis of variance, P <0.001) and greater in men (7.4 +/- 2.4) than in women (6.7 +/- 2.5) (t-test, P <0.001). In a Cox model adjusted for potential confounders, SAI was associated with decreased mortality [hazards ratio of 0.97 (95% confidence interval 0.95-0.99), P = 0.006]. Subgroup analysis demonstrated an association of SAI with survival in most of the subgroups. Potential limitations of the study include reverse causality, possible misclassification and retrospective design. Conclusion. We demonstrated that SAI is significantly associated with mortality in dialysis patients. SAI could be used to identify individuals at risk for inferior clinical outcomes.