Case aggregation in young adult Hodgkin's disease. Etiologic evidence from a population experience

There is evidence to suggest that young adult Hodgkin's Disease (HD) may be initiated by an infectious process and that age at exposure to the etiologic infection is an important modifier of risk. There is little evidence, however, to suggest that HD is transmissible through interpersonal contact. To evaluate this hypothesis, a population-based case-control study was conducted with 103 HD cases diagnosed between January 1, 1974 and June 30, 1979 in King County, Washington. Its purpose was to determine whether cases aggregate before clinical disease through interpersonal contact in either school or employment settings to a greater degree than would be expected in the general population. One control was randomly selected for each case of the same sex, approximate age, and general socioeconomic level. Results showed no indication of case aggregation in employment settings (observed/expected = 0.77; P = 0.77). Case contact was greater than would be expected in schools (observed/expected = 1.2; P = 0.07), particularly in grade schools (observed/expected = 1.94; P = 0.009). This finding is consistent with the possibility that HD is dependent on age at exposure, has an infectious origin, and can be transmitted horizontally in select circumstances. Additional research possibilities are recommended as suggested by these data.