Prevalence of autoimmune diseases is strongly associated with average annual temperatures: systematic review and linear regression analysis

Background: The incidence of autoimmune diseases in cold environments has been a topic of interest due to the observed geographical patterns and potential environmental influences on disease development. We aimed to investigate the prevalence of five main autoimmune diseases in 201 countries according to average annual temperatures. Methods: Linear regression analysis was performed for 201 countries by analyzing average annual temperatures and age-standardized rates (prevalence) of five autoimmune diseases: alopecia areata, diabetes mellitus (DM) type 1, inflammatory bowel disease (IBD), psoriasis and rheumatoid arthritis (RA). A systematic review was also conducted to evaluate whether the observed correlations were supported by published original studies. Results: The linear regression analysis showed a strong correlation between average annual temperatures and age-standardized prevalence rates (p < 0.0001) across 201 countries. The systematic review analysis indicated that certain autoimmune diseases, such as DM type 1, RA, psoriasis and IBD, demonstrate robust associations with geographic and climatic factors. However, there were no available published data for alopecia areata. Conclusions: These findings underscore the complexity of interactions between environmental, and genetic factors in the development of autoimmune diseases. Further investigation is required to better understand the association between temperature and prevalence of autoimmune diseases and to identify any additional epidemiological factors that contribute to autoimmune pathogenesis.