Sex-specific mortality from adult T-cell leukemia among carriers of human T-lymphotropic virus type I.

Perinatal infection with human T-lymphotropic virus type I (HTLV-I) is considered a risk factor for adult T-cell leukemia (ATL). Incidence of ATL in Japan is generally higher in males compared with females, perhaps partly due to an earlier average age of infection among males. We estimated sex-specific ATL mortality among perinatally-infected HTLV-I carriers in the prospective Miyazaki Cohort Study in Japan. Based on the approximated proportion of perinatally-infected carriers, the relative risk (RR) of ATL for males compared with females was calculated. Six ATL deaths (4 males, 2 females) occurred among the 550 HTLV-I carriers in the cohort during 13 years of follow-up. The overall ATL mortality was 190.5 (95% CI 51.9-487.7) per 10(5) person-years for males and 51.7 (6.3-186.8) per 10(5) person-years for females (age-standardized RR = 3.9, p=0.02). By approximating the number of persons who acquired infection perinatally, the estimated mortality among those perinatally-infected HTLV-I carriers was 209.1 (57.0-535.2) per 10(5) person-years for males and 60.9 (7.4-219.9) per 10(5) person-years for females (age-standardized RR = 3.7, p=0.02). The adjusted RR changed minimally from the unadjusted RR, suggesting that earlier age of infection alone is unlikely the explanation for the male predominance in ATL. Based on the small number of cases available for analysis, aspects of gender itself appear to play a role in the development of this malignancy.