Mycobacterium tuberculosis infection and the subsequent development of asthma and allergic conditions.

Epidemiologic studies have suggested that certain viral infections, as well as exposure to Mycobacterium tuberculosis in early life, could, at least to some extent, prevent the subsequent development of atopic disease. We investigated whether M tuberculosis infection in childhood or adolescence has any effect on the development of asthma and allergic conditions in later life. The study subjects (n = 1162) were individuals notified to the National Tuberculosis Registry between January 1, 1966, and December 31, 1969, who were 20 years of age or younger and had verified or justifiably probable new active tuberculosis of respiratory or other organs. The control subjects were age-matched, sex-matched, and geographically matched control pairs from the Population Registry of the Social Insurance Institution in Finland. The subjects were followed for 28 to 32 years. The prevalence of persistent asthma and allergic conditions among men and women at the end of 1997 were calculated on the basis of the Drug Reimbursement Registry of the Social Insurance Institution in the whole study population and in the subgroup of subjects aged 16 years or younger at the time of M tuberculosis infection. In women a significantly lower prevalence of persistent asthma was found among those aged 16 years or younger at the time of M tuberculosis infection than among the control subjects (3.7% vs 8.3%, respectively; P =.035). The women with a history of tuberculosis also showed a significantly lower prevalence of allergic conditions than the control subjects (8.3% vs 14.0%, respectively; P =.003) when the whole study population of women was considered. In men, however, the only significant difference between the cases and control subjects was found for persistent asthma, with the cases showing a significantly higher prevalence than the control subjects (4.4% and 1.8%, respectively; P =.008). M tuberculosis infection in childhood significantly reduced the occurrence of subsequent asthma in women. Moreover, this infection was also found to reduce the occurrence of allergic conditions in later life in women. By contrast, no suppressive effect of M tuberculosis infection in childhood or adolescence on the later development of asthma or allergic conditions could be observed in men. The differences in the natural history of atopic disease between the sexes and the occurrence of tuberculosis mostly in later childhood and adolescence may largely explain our findings.