Clustering of Hodgkin's disease in Israel: a case-control study

The geographical distribution of Jewish patients in Israel with HD diagnosed between 1960 and 1972 differed significantly from that of individually-matched population controls. Significant clustering occurred in 3 regions of the country. The odds ratio expressing the greater tendency of patients to have lived in one of these regions 5-9 years before the diagnosis, as compared with that of their paired controls, was 2.4. The association with residence in a higher-risk region was not significantly modified by sex, age, period of immigration, region of birth, father's region of birth, or date of diagnosis. The association was weaker for cases with nodular sclerosis than for those with other subtypes of HD. The clustering could not be explained by available data on the characteristics and prior experience of the cases and controls. There was a significant correlation between the risk of HD in a region and the proportion of native Israelis in its Jewish population, but there were no significant correlations with a variety of other demographic, natural and socioeconomic features of the regions. There was no significant time-space interaction. The findings suggest that susceptible people living in certain parts of the country during the 1950's and 1960's had a somewhat enhanced risk of HD because of exposure to unidentified environmental factors active in those regions at that time.