Benchmarks for interpretation of score differences on the SF-36 health survey for patients with diabetes.

OBJECTIVE: To estimate clinical and social benchmarks for interpretation of score differences on the Short-Form 36 Health Survey, and apply these benchmarks to populations with diabetes mellitus (DM).
METHODS: Using survival and logistic regression models, we reanalyzed data from three US cohorts: the Medical Outcomes Study (N = 3,445; 541 patients with DM), the Medicare Health Outcomes Survey (N = 78,183; 16,388 patients with DM), and the QualityMetric 2009 Norming Study (N = 4,040; 580 patients with DM). Outcome variables were mortality, hospitalization, current inability to work, and loss of ability to work.
RESULTS: Benchmarks were robust across disease groups, but varied according to age and score level. A 1-point lower score on the Physical Function, General Health, and Physical Component Summary scales was associated with a 1.05 to 1.09 relative risk (RR) of mortality for the typical patient with DM, with stronger associations in the younger age groups. For several scales (Physical Function, Role Physical, Bodily Pain, General Health, Vitality, Social Function, and Role Emotional), the associations with mortality also depended on score level, with stronger associations in the lower score ranges (i.e., patients in worse health). A 1-point lower score on the Physical Function, Role Physical, Bodily Pain, General Health, Vitality, Social Function, and Physical Component Summary scales implied a 1.02 to 1.04 RR of hospitalization, a 1.07 to 1.12 RR of being unable to work, and a 1.04 to 1.07 RR of losing the ability to work.
CONCLUSIONS: A 1-point lower score on selected Short-Form 36 Health Survey scales is associated with an excess risk of up to 9% for mortality and 12% for inability to work.