This study was aimed at determining whether the familial clustering often observed in breast cancer is associated with genetic factors. We compared familial and sporadic breast cancer cases with respect to ABO blood group distribution and the risk of bilateral disease, using the data from the Icelandic Cancer Registry which contains genealogical information for about 30% of the breast cancer cases diagnosed in Iceland since 1911. Cases were classified as familial if at least one first-degree relative had breast cancer. Using this criterion, we identified 184 familial cases and 572 sporadic cases. The familial cases had a 2-fold higher prevalence of blood group B than did the sporadic cases, and the frequency of this blood group in non-affected relatives of cases was significantly reduced. Familial cases were about 2.7 times more likely to suffer from bilateral breast cancer than were the sporadic patients. These results support the presence of a genetic factor in the etiology of familial breast cancer.
The epidemiology of dementia in Canada is not known. However, we report figures on the frequency of dementia in institutions in Ontario based upon the use of a multidimensional observation scale for the assessment of the elderly. These findings on institutionalized patients can be extrapolated to the whole elderly population, but the procedure is clearly too conservative by comparison with findings in other countries and in the light of the known occurrence of numbers of demented patients outside institutions. Ratios in different studies for the numbers of patients with dementia outside institutions and within institutions range from 1:1 to 6:1. Using a ratio of 2:1 and applying it to age specific population figures, a prevalence of dementia in Canada of 222,324 for those over 65 is obtained with a rate of 9.4% in that age group. When the figures projected in this way are compared with five epidemiological studies for the rate of dementia elsewhere, the Canadian figure which we have obtained ranks fourth out of six. This estimate provides potential figures on which to base the planning of services, provided that the inferential nature of the estimates is fully recognized.
This study examined the possibility that lead pipes in the drinking water distribution system were elevating the blood lead levels of children in London, Ontario, Canada. Based on their postal codes, 164 children admitted between 1984 and 1989 to an institution for the behaviorally disordered or developmentally challenged were categorized according to whether they lived in the area of the city known by the local Public Utilities Commission to be serviced by lead pipes. Analysis of covariance was used to obtain confounder-adjusted geometric means in each area. After adjusting for gender, year of lead test (a surrogate for gasoline source), and census tract prevalence of low family income, children in the lead service area (LSA) were found not to have higher blood lead levels (geometric means: LSA = 4.7 micrograms/dl, Non-LSA = 4.8 micrograms/dL; p = 0.839). The average blood lead level declined 60.9% between 1984 and 1989. Using municipal tax assessment data on the age of each child's home, those children living in homes built during or before 1945 (when interior paints were as much as 50% lead by dry weight) had an average blood lead level that was 62.3% higher (p = 0.011) than that of those in homes built since 1975 (when interior paints were limited to no higher than 0.5% lead by dry weight). A clear gradient was observed. This association with age of home remained significant after adjusting for gender, diagnosis, and year of lead test. Variables indicating the amount of industry near the child's residence and the presence of lead service pipes did not enter the model after house-age. In conclusion, no evidence indicated that the lead service pipes were elevating blood lead levels in these London children. The data suggest that with the removal of lead from gasoline, lead-based paint is a significant remaining source of lead exposure. Little data are available on childhood lead exposure from paint in Canada. The present descriptive data suggest that more research into this potential problem in Canada is warranted.