Background: Several large cohort studies suggest that patients with type 1 diabetes are at increased risk of all-cause and cardiovascular mortality. Despite this, little is known about the clinical predictors for mortality and first cardiovascular event in Australian patients with type 1 diabetes.
Methods: We undertook a retrospective longitudinal cohort study linking clinical data captured from patients with type 1 diabetes attending Royal Melbourne Hospital outpatient clinics from 1998 to November 12 2016 (using the BioGrid diabetes database), with hospital separation data and the Australian National Death Records..
Results: Overall 107 of the 1,420 patients with type 1 diabetes died during the follow-up period, and 85 patients in the cohort suffered their first cardiovascular event. The mean follow-up was 9.6 years and mean age at diagnosis 18.7 years. Multivariate regression analysis demonstrated an adjusted hazard ratio for all-cause mortality of 2.34 (95% CI, 1.08 to 4.98) for patients with HbA1c of <7% and 2.28 (95% CI, 1.42 to 5.42) for patients with HbA1c levels of ≥9% compared with those with levels of 7-8%. Adjusted hazard ratios for all-cause mortality compared to those without albuminuria were 2.24 (95% CI, 1.34 to 3.72) for and 2.67 (95% confidence interval 1.39 to 5.14) for those with microalbuminuria and macroalbuminuria, respectively. Corresponding adjusted hazard ratios for first cardiovascular event were 2.19 (95% CI, 1.06 to 4.53) for patients with macroalbuminuria.
Conclusions: Concordant with other cohort studies, our data demonstrated that in Australians with type 1 diabetes, both HbA1c levels ≥9%, and also those <7% were associated with greater than twice the risk of death. Other clinical predictors for death included both micro- and macroalbuminuria. Furthermore, in our study, macroalbuminuria conveyed the largest risk of developing first cardiovascular event, even following adjustments for other clinical risk factors.