Sex Differences in Autoimmune Multimorbidity in Type 1 Diabetes Mellitus and the Risk of Cardiovascular and Renal Disease: A Longitudinal Study in the United States, 2001–2017

Background: Autoimmune diseases are usually more prevalent in women. The risks of cardiovascular and renal disease in those with multiple autoimmune diseases have not been fully described. Materials and Methods: Using a national database from a large health insurer in the United States (years 2001-2017) containing ∼75 million members, we calculated age- and sex-specific co-prevalence of 12 autoimmune disorders for individuals with type 1 diabetes. We then evaluated whether concomitant autoimmune diseases were associated with renal failure, ischemic stroke, and myocardial infarction. Results: Of the 179,248 people diagnosed with type 1 diabetes, 1 in 4 had a concomitant autoimmune disease (27.03%; 95% confidence interval [CI] = 26.83%-27.24%), with hypothyroidism, rheumatoid arthritis, and celiac disease being the most common. The prevalence of autoimmune disease was 1.9 times greater in female than male patients ( p  < 0.001). In female patients with type 1 diabetes, one in three had another autoimmune disease (35.62%; 95% CI = 35.30%-35.94%) compared with one in five male patients (19.17%; 95% CI = 18.92%-19.42%). The risk of renal failure, ischemic stroke, and myocardial infarction increased with a greater number of concomitant autoimmune diseases ( p  < 0.001, test for trend for both female and male patients). Patients with type 1 diabetes who had multiple sclerosis or myasthenia gravis experienced an approximate threefold increase in risk of ischemic stroke (odds ratio [OR] = 3.57, OR = 3.22, respectively). Patients with type 1 diabetes and Addison's disease had a threefold increased risk of renal failure. Conclusions: Patients with type 1 diabetes, particularly women, frequently have coexisting autoimmune diseases that are associated with higher rates of renal failure, ischemic stroke, and myocardial infarction. Additional study is warranted, as are preventive efforts in this high-risk population.