Predictive Validity of Each Item of the 8-Item Short-Form Health Survey for All-Cause Mortality in Japanese patients with type 2 diabetes: A prospective Cohort Study (Diabetes Distress and Care Registry at Tenri [DDCRT 19])

Abstract

Aims: While health-related quality of life (HRQOL) is reported to be associated with mortality, this assessment was made using surveys with a large number of questions, not specifically focused on populations with diabetes, or in western countries alone. We thus evaluated the predictive validity of summary scores, and each item score of the 8-Item Short-Form Health Survey in Japanese individuals with type-2 diabetes.

Materials and methods: Longitudinal data from 3269 individuals with diabetes were obtained from a large Japanese diabetes registry. To assess the independent correlation between the 10-point scores of the SF-8 physical component summary (PCS) and mental component summary (MCS), each item score, and all-cause mortality, the Cox proportional hazards model was used with adjustment for potential confounders.

Results: Mean cohort parameters included age (64.9 years [SD 11.2]), body mass index (24.6 kg/m² [SD, 3.9]), and HbA1c level (7.5% [SD, 1.2]; or 58.6 mmol/mol [SD, 12.7]). We recorded 248 deaths during the median follow-up of 7.2 years (incidence ratio, 12.2 per 1000 person-years). Multivariable-adjusted HRs for all-cause mortality were 0.780 (95%CI, 0.674-0.902; p=0.001) and 0.776 (95%CI, 0.656-0.917; p=0.003), respectively, for 10-point increment of PCS and MCS scores. Higher score of any single item of SF-8 was associated with lower risk of all-cause mortality even after adjusting for possible confounders.

Conclusions: As assessed by the SF-8, higher PCS, MCS, and any single 1-item scores were associated with lower risk of all-cause mortality in Japanese individuals with type 2 diabetes.