Method of Statistical Analysis of Chronic Disease in a Longitudinal Study of Illness

rT HE purpose of this paper is to present a detailed description of the method employed in the statistical treatment and presentation of data of chronic disease reported in the study of illness in the Eastern Health District of Baltimore (1). White families living in thirty-four city blocks formed the sample population. The plan of the study was to follow families that lived in a group of houses in certain blocks rather than to follow a selected group of families. No attempt was made to continue visiting families which moved out of these houses during the period of the study, but the new families that moved into the houses vacated in the sample blocks were included in the study. The record of illness started with the first visit to the family and each family was visited once a month thereafter.