Comparative mortality and its determinants in community-based people with type 1 diabetes: the Fremantle Diabetes Study Phase I

Abstract

Introduction The aim of this study was to compare mortality in community-based Australians with type 1 diabetes (T1D), without diabetes, or with type 2 diabetes (T2D).Research design and methods The longitudinal observational Fremantle Diabetes Study Phase I (FDS1) T1D cohort, matched people without diabetes from the FDS1 catchment area, and matched FDS1 participants with T2D were followed up from entry (1993–1996) to death/end-2017. Mortality rates (MRs) and mortality rate ratios (MRRs) were calculated. Cox regression models identified independent determinants of death.Results Of 121 participants with T1D and 484 age/sex/postcode-matched people without diabetes (pooled mean±SD age 43.1±15.3 years, 59.2% men), 55 (45.5%, MR 25.7 (95% CI 19.4 to 33.5)/1000 person-years) and 88 (18.2%, MR 8.5 (95% CI 6.8 to 10.4)/1000 person-years), respectively, died during 12 541 person-years of follow-up (MRR 3.04 (95% CI 2.13 to 4.31), p<0.001). Among participants with T1D, diagnosis at age 18–27 years and baseline HbA1c, urinary albumin:creatinine ratio, and retinopathy were independent predictors of death (p≤0.011). Twenty-five FDS1 participants died from cardiovascular disease (MR 11.7 (95% CI 7.6 to 17.3)/1000 person-years) vs 28 residents without diabetes (MR 2.7 (95% CI 1.8 to 3.9)/1000 person-years; MRR (95% CI) 4.34 (2.43, 7.73) (p<0.001). There were 93 FDS1 participants with T1D who were age/sex matched with an FDS1 participant with T2D and 53 (57.0%) and 37 (39.8%), respectively, died (p=0.027). In pooled Cox regression analysis, T1D was not a determinant of mortality (HR 1.18 (95% CI 0.71 to 1.97), p=0.523).Conclusions T1D substantially increases the risk of death, especially when diagnosed in late adolescence/young adulthood. Diabetes type does not influence mortality after adjustment for key confounding variables.