Time trends in deaths before age 50 years in people with type 1 diabetes: a nationwide analysis from Scotland 2004-17

Objective: To examine whether crude mortality, and mortality relative to the general population below 50 years of age has improved in recent years in those with type 1 diabetes.
Methods: Individuals with type 1 diabetes aged below 50 and at least 1 year old at any time between 2004-2017 in Scotland were identified using the national register. Death data were obtained by linkage to Scottish national death registrations. Indirect age standardisation was used to calculate sex-specific standardised mortality ratios (SMRs). Poisson regression was used to test for calendar time effects as incident rate ratios (IRR).
Results: There were 1138 deaths in 251143 person years among 27935 people with type 1 diabetes. There was a significant decline in mortality rate over time (IRR for calendar year = 0.983, 95% CI = 0.967-0.998, p=0.03) but the SMR remained approximately stable at 3.1 and 3.6 in men and 4.09 and 4.16 in women for 2004 and 2017 respectively. Diabetic ketoacidosis or coma (DKAoC) accounted for 20.8% of deaths and the rate did not decline significantly (IRR=0.975, 95% CI 0.94-1.011, p=0.168); 79.3% of DKAoC deaths occurred out of hospital. Circulatory diseases accounted for 27.6 % of deaths and did decline significantly (IRR=0.946 (95% CI 0.914-0.979), p=0.002).
Conclusions: Absolute mortality has fallen, but the relative impact of type 1 diabetes on mortality below 50 years has not improved. There is scope to improve prevention of premature circulatory diseases and DKAoC and to develop more effective strategies for enabling people with type 1 diabetes to avoid clinically significant hyper- or hypoglycaemia.