Aims To examine all‐cause and cause‐specific mortality in a population‐based cohort of people with early and late onset of Type 1 diabetes. Methods The Yorkshire Register of Diabetes in Children and Young People includes individuals with early (0–14 years) and late (15–29 years) Type 1 diabetes onset, diagnosed between 1978 and 2013. This register was linked to death certification data from the Office for National Statistics to calculate standardized mortality ratios, cumulative mortality curves using Kaplan–Meier survival estimates, and Cox regression modelling. Ethnicity was derived using Onomap. Deprivation status was classified using the Townsend index. The underlying cause of death in each case was clinically verified. Results There were 229 deaths in 5498 individuals with 100 959 person‐years of follow‐up. The overall standardized mortality ratio was 4.3 (95% CI 3.8 to 4.9). There were no significant differences in standardized mortality ratios according to age of onset, sex or deprivation status. The standardized mortality ratios were significantly higher for people of white ethnic origin [8.1 (95% CI 6.9 to 9.4)] than for those of South‐Asian ethnic origin [3.4 (95% CI 1.7 to 6.4)]. The mortality risk was lower in those diagnosed in later years (2002 to 2013 for the early‐onset and 2006 to 2013 for the late‐onset group) compared with earlier years (1991 to 1997 for the early‐onset and 1991 to 1997 for the late‐onset group) for both onset groups [hazard ratio 0.13 (95% CI 0.05 to 0.33) vs 0.24 (95% CI 0.07 to 0.81)]. Mortality risk improved over time for chronic complications in the early‐onset group only, but there was no improvement in either onset group with regard to acute complications. Conclusions An excess of deaths in the population with Type 1 diabetes remains. Although the all‐cause mortality risk has fallen over time, no improvement has been found in the mortality risk associated with acute complications.
