Increased risk of mortality and readmission associated with lower SF-12 scores in cardiac patients: results from the national DenHeart study

Background: The SF-12v2 health survey (SF-12) is widely used as a generic measure of health-related quality of life. However, interpretation of score differences can be difficult. Aim: To estimate benchmarks for interpretation of score differences on the SF-12 for readmission and all-cause mortality in cardiac patients. Methods: Data from the DenHeart study, a national cross-sectional survey including one year follow-up register data, were used. Patients with ischaemic heart disease, arrhythmia, heart failure and heart valve disease answered the survey at hospital discharge. Cox proportional hazards models were used to regress readmission and all-cause mortality. Results: A total of 10,813 cardiac patients completed the SF-12. For patients with ischaemic heart disease and arrhythmia, a one point lower physical component summary score was associated with a 2% increase in risk in readmission (hazard ratio (HR) 1.022 (95% confidence interval 1.017;1.027) and HR 1.024 (1.018; 1.029), respectively) and a 3% increase in risk for patients with heart failure (HR 1.027 (1.015; 1.038)). A one point lower mental component summary score was associated with a 2% increase in the risk of readmission (HR 1.017 (1.013; 1.022)) across diagnoses. For both the physical and mental component summary score, a one point lower score meant a 5% increase in the risk of all-cause mortality (HR 1.046 (1.031; 1.060) and HR 1.046 (1.029; 1.065), respectively) across diagnoses. Conclusion: In a large group of cardiac patients, a one point lower physical or mental component summary score was associated with an up to 3% increased risk of readmission and a 5% increased risk of mortality in the first year after discharge.