A follow-up study of the commission on chronic illness morbidity survey in Baltimore—III: Residential mobility and prospective studies

Abstract

Residential mobility of the study population is an important factor to be anticipated and planned for in the conduct of prospective studies. Here we have presented data on residential mobility among the Baltimore City survey population originally interviewed by the Commission on Chronic Illness in 1953–1954 and followed for address and survivorship in 1960–1962. Within this interval, averaging around 6 yr, over half the whites and two-thirds of the non-whites had changed residences. Variation by race, age, and to some extent socio-economic status, was observed in both the volume of mobility and the destination of movers. The experience gained in our study suggests that in a prospective study of a large central city population, the greatest effort must be expended in tracing persons who move within the central city rather than beyond its limits, and this is particularly the case of the non-white population who move frequently but for whom restrictions have prevented movement into the fringes of metropolitan areas. The problem of tracing persons to out-of-state destinations was relatively minor for both whites and non-whites. Our findings indicate also that when matched by age, hospitalized persons, often the subjects for prospective studies, have roughly the same residential mobility patterns as persons who have not been hospitalized. Thus, in terms of ease of tracing, such persons present no particular advantage. Some information has been presented to show that attrition in the study population, largely through residential mobility, can alter the results of research investigations. With near-complete follow-up of our population, we found no race differences in mortality within our sample. However, had our analysis been based on a follow-up terminated at a point where we began to employ intensive measures to reach the “hard-core”, we would have found race differences in mortality among females. Last, because white out-migrants appear to be selective of persons with lower mortality, it has been suggested that the total death rate of Baltimore City, as well as race differences in death rates, may have been affected by migration patterns.