AN ANALYSIS OF EXCESS MORTALITY-RATES FOR PERSONS WITH NON-INSULIN-DEPENDENT DIABETES-MELLITUS IN WESTERN AUSTRALIA USING THE COX PROPORTIONAL HAZARDS REGRESSION-MODEL

A cohort of 888 rural, nonaboriginal persons with non-insulin-dependent diabetes mellitus identified in Western Australia through surveys in 1978-1982 were followed for death until the end of 1986. A total of 257 deaths were observed. Excess mortality in this cohort as compared with the general Australian population was investigated by calculating standardized mortality ratios and using the Cox proportional hazards regression model with hazard rates for the general population as the baseline. The overall standardized mortality ratio was 1.83 (95% confidence interval 1.51-2.16) for women and 1.43 (95% confidence interval 1.18-1.67) for men. Cause-specific comparisons with the general population showed that the majority of excess deaths could be attributed to diseases of the circulatory system. Factors assessed at the baseline survey that were independently prognostic of shorter survival were early onset of diabetes (for females only), high plasma glucose level, retinopathy, macrovascular disease, albuminuria (for females only), and elevated plasma creatinine level. Reductions in life expectancy at 60 years of age as compared with the general population averaged about 5 years but could be as much as 16 years for female diabetics with early onset of diabetes, high plasma glucose levels, and several complications.