Effect of birth season on case fatality rate of pulmonary tuberculosis: coincidence or causality?

Abstract The effects of birth season on the case fatality rate (CFR) of pulmonary tuberculosis were examined in case records of 9206 patients discharged during 1937–1965 from a national hospital for tuberculosis in Tokyo. The CFR was over 60% until 1945, then it decreased down to less than 9% after 1950. Male cases had little variation in their CFR by their birth season, while female cases had a significant variation and showed a significantly higher CFR than the male cases when they were born in January–June. The results suggest that the birth season had a significant influence on the prognosis of pulmonary tuberculosis.