Subsequent autoimmune or related disease in asthma patients: clustering of diseases or medical care?

PURPOSE: Asthma includes immunological components that may share mechanisms with autoimmune diseases. We analyzed the subsequent occurrence of any of 22 autoimmune and related conditions in hospitalized asthma patients.

METHODS: A nationwide study was conducted in Sweden on subsequent diseases of asthma patients on the basis of the Hospital Discharge Register. Standardized incidence ratios (SIRs) were calculated for subsequent autoimmune diseases.

RESULTS: A total of 4006 patients were hospitalized for an autoimmune condition after last hospitalization for asthma. The SIRs were increased for 11 subsequent autoimmune conditions, diagnosed at least 5 years after asthma. The highest SIRs were noted for polyarteritis nodosa (4.29) and Addison disease (3.62). SIRs for these diseases and others, including the most common autoimmune disease rheumatoid arthritis, were increased even when the follow-up was started 5 years after the last asthma hospitalization. Addison disease and Crohn disease were increased in asthma patients hospitalized at various ages, whereas young asthma patients presented with celiac disease and immune thrombocytopenic purpura.

CONCLUSIONS: Hospitalized asthma patients presented with a number of subsequent autoimmune and related diseases. Although we were unable to exclude the effects of environmental factors, the data suggest that shared genetic factors or gene-environment interactions may explain coexistence of some of these diseases.