Similar geographic distributions of death rates from inflammatory bowel disease and Hodgkin lymphoma or multiple sclerosis

BACKGROUND: A previous comparative analysis of the time trends of Hodgkin lymphoma (HL), multiple sclerosis (MS), Crohn's disease (CD), and ulcerative colitis (UC) suggested that the occurrence of all four diseases was precipitated by exposure to similar environmental risk factors during early lifetime. In the present cross‐sectional study, it was hypothesized that besides their resembling temporal variations the four diseases would also show similar geographic distributions. METHODS: Using the vital statistics of 21 countries from 1951 to 2020, overall and age‐specific death rates from the four diseases were calculated for each individual country. The death rates of different countries were compared using linear regression analysis. RESULTS: The data revealed strikingly similar geographic distributions of all four diseases. Their occurrence was common in Europe and relatively uncommon in countries outside Europe. Further stratification by consecutive age groups showed that for each disease analyzed separately, there were significant correlations amongst each two sequential age groups. In HL and UC, the inter‐age correlations started at age 5 years or less. In MS and CD, the inter‐age correlations only started at age 15 years. CONCLUSIONS: The similarities in the geographic distributions of death rates from HL, MS, CD, and UC suggest that these four diseases share a set of one or more common environmental risk factors. The data also support the contention that the exposure to such shared risk factors starts during an early period of lifetime.