Findings from the Miyazaki Cohort Study.

The purpose of the Miyazaki Cohort Study is to describe and analyze the natural history of human T-cell lymphotropic virus type I (HTLV-I) in a highly endemic population in southwestern Japan. As of August 1995, 1,960 individuals have been enrolled, of whom 27% were HTLV-I antibody positive at baseline. Our achievements over the past decade of following this cohort include the identification of several viral markers that characterize high-risk carriers and the documentation that carriers have subclinical evidence of impaired cellular immunity. We have begun to estimate the impact of the infection on the health of carriers and have found that men are at greater risk of HTLV-I-associated diseases than women. We have been able to identify prospectively risk factors associated with sexual transmission. Most important, by identifying subclinical markers of pathogenesis, we hope to provide the foundation for developing interventions to prevent HTLV-I-associated disease.