Chantzichristos D, et al. - Among persons with or without type 1 diabetes mellitus (T1DM) in nationwide, matched cohort studies, the researchers aimed to determine the incidence and prevalence of Addison's disease (AD). In persons with T1DM, the risk to develop AD was more than 10 times higher than in persons without T1DM. AD was developed at a younger age in persons with T1DM. The incidence of AD could have a seasonal pattern.

• The researchers identified persons with T1DM from the Swedish National Diabetes Register and each was matched for age, sex, year, and county to 5 controls randomly selected from the general population.
• From the Swedish National Inpatient Register, persons with AD were identified.
• By descriptive statistics, baseline demographics and seasonal onset variation of AD were presented.
• They estimated prevalence and incidence by proportions and incidence rates, respectively.
• Cox proportional hazards model was used to examine time to AD.

• While 32 persons were diagnosed with AD at a mean age of 42.7 (15.2) years among 182,570 controls, 66 persons with T1DM were diagnosed with AD at a mean age (S.D.) of 36.4 (13.0) years among 36,514 persons with T1DM between 1998-2013.
• Between the groups, the difference in mean age at diagnosis of AD was 6.3 years (p value=0.036).
• Therefore, the incidence of AD for a person with or without T1DM was 193 and 18 per million person-years, respectively.
• In T1DM, the adjusted relative risk increase of developing AD was 10.8 (95% CI: 7.1-16.5).
• During February-March and September-October, the highest incidence of AD was observed.
• At December 2012, the prevalence of AD in persons with or without T1DM was 3410 and 208 per million, respectively.
• For AD, the odds ratio in persons with T1DM vs controls was 16.5 (95% CI: 11.1-24.5).