Type 1 diabetes incidence in Scotland between 2006 and 2019.

Aims: To describe type 1 diabetes incidence in Scotland between 2006 and 2019.

Methods: Repeated annual cross-sectional studies of type 1 diabetes incidence were conducted. Incident cases were identified from the Scottish Care Information-Diabetes Collaboration (SCI-DC), a population-based register of people with diagnosed diabetes derived from primary and secondary care data. Mid-year population estimates for Scotland were used as the denominator to calculate annual incidence with stratification by age and sex. Joinpoint regression was used to investigate whether incidence changed during the study period. Age and sex-specific type 1 diabetes incidence over the whole time period was estimated by quintile of the Scottish Index of Multiple Deprivation (SIMD), an area-based measure, in which Q1 and Q5 denote the most and least deprived fifths of the population, respectively, with quasi-Poisson regression used to compare incidence for Q5 compared to Q1.

Results: The median (IQR) age of the study population of 14,564 individuals with incident type 1 diabetes was 24.1 (12.3-42.4) years, 56% were men, 23% were in Q1 and 16% were in Q5. Incidence of T1DM was higher in men than women overall (at around 22 and 17 per 100,000, respectively) and in under 15 year olds (approximately 40 per 100,000 in both sexes) than other age groups and was similar across the study period in all strata. There was an inverse association between socio-economic status and type 1 diabetes incidence for 15-29, 30-49 and 50+ year olds [incidence rate ratio (IRR) for Q5 compared to Q1; IRR (95% CI) 0.52 (0.47-0.58), 0.68 (0.61-0.76) and 0.53(0.46-0.61), respectively] but not for under 15 year olds [1.02 (0.92-1.12)].

Conclusion: Incidence of type 1 diabetes varies by age, sex and socio-economic status and has remained approximately stable from 2006 to 2019 in Scotland.