vival chances. For instance, the Haiti project shows how research and services contribute to each other.
Prospective community studies have demonstrated clearly how biological and social processes are intertwined. A number of results on the behavioural determinants of health emerged from these studies. For example, we learned a great deal about the gender bias in South Asia from the studies in Khanna and Matlab. Death-clustering, a new area of research in the field of demography and child survival, also originated in Khanna-II. The Haiti Study showed that marriage patterns, child-fostering, and migration are also major determinants of health: indications of this emerge from cross-sectional studies, but could be explored convincingly only with the use of prospectively collected data.
Most of these studies focus on the health of children below the age of 5. In most of the study sites, deaths in this age-group accounted for more than half of the deaths of all ages combined. In comparison, little research has been conducted on the health of young adults, with the exception of maternal mortality. With the emergence of AIDS and the re-emergence of other sexually transmitted diseases and of tuberculosis, there is a renewed interest in the health of young adults. The Pholela Study, which was conducted in a more economically advanced country, addressed these issues and showed how much could be gained by working closely with the community.
Although relatively costly and time-consuming, there is no doubt that these studies were worth undertaking and are worth pursuing. Their legacy certainly shows them to be extremely worth-while research enterprises, as our basic knowledge of health processes would be far more deficient if they had not been undertaken. Much knowledge which has become standard input to understanding health processes and to policy-making would never have come without these longitudinal studies. They provided a scientifically documented rationale for many health interventions, which otherwise may not have been made or been based on inadequate information.
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