Early studies of tuberculosis.

Cohort studies have been of great importance in the establishment of what is known about the epidemiology of tuberculosis. The individuals who conducted these studies provided useful models for the application of life table, person-time, and cohort analyses to the study of diseases. These tuberculosis workers not only have shown that follow-up of large cohorts can be virtually complete, but, even more importantly for future cohort studies, they have also shown how cohort investigations can be done at minimal expense.