Vasectomy and prostate cancer in Québec, Canada.

The present investigation measured the association between vasectomy and prostate cancer (PC) in the male population of Québec, Canada. The Québec Health Insurance Board and the Québec Cancer Registry were our principal sources of information. Lung cancer cases and the male population of Québec served as controls for comparative purposes. Within a retrospective design, our preliminary results indicate an association between vasectomy and PC. Among the 1925-39 birth cohort of individuals diagnosed with PC in 1990--93, the global odds ratio was 2.6 (95% CI=1.7--4.3) while it was compared with lung cancer as the control group. This risk increased with the length of time between vasectomy and the diagnosis of cancer. An historical design indicated strong cohesion of the results. Besides, the risk does not vary when we control for the place of residence of the individuals. Vasectomy seems to increase the risk of PC at least 10 years after the operation, but we cannot exclude the impact of a possible detection bias among vasectomized individuals.

[CO2 laser skin resurfacing. Critical analysis of recent literature]. / Traitement au laser CO2 des imperfections cutanées. Analyse critique de la littérature récente.

Over recent years, there appears to have been an explosion of public interest in facial rejuvenation. With the recent development of short-pulsed high-peak power and rapidly scanned carbon dioxide (CO2) lasers, it is now possible to remove photo-damaged skin precisely and reproducibly, while leaving behind a narrow zone of thermal damage. This development has generated tremendous interest in laser skin resurfacing as a technique to reverse photoaging. However, the overall review of the existing literature, except for very few publications, reveals several major methodological problems. The use of CO2 laser for cosmetic purposes is very recent and therefore requires further justification, standardization and regulation based on well designed studies. Most of the recent published data correspond to case reports, rather than well-designed scientific studies. For these reasons, this field needs more clinical trials and epidemiological investigations such as prospective cohorts or case-control studies, to provide new knowledge in this field.

[Spatial/temporal analysis of the incidence of certain cancers by sites in Quebec: 1984-1986 and 1989-1991]. / Analyse espace/temps de l'incidence de certains sièges de cancer au Québec: 1984-1986 et 1989-1991.

Basing our views on recent works of an Ontarian research group, we analyze the profiles of incidence of the main types of cancers observed in the province of Québec for the periods 1984-1986 and 1989-1991. Using the Québec Tumors Registry, we have calculated standardized incidence rates according to sex for each of the 32 departments of community health in the province. A geographical analysis of cancers was conducted via two methods of spatial autocorrelation (SA). Many cancer sites (i.e., breast, lung, stomach) show a positive SA (p < 0.05), indicating an aggregation of cases. Several aggregation schemes observed in Québec resemble those observed in Ontario. In women, the highest incidence rate increases are in leukemia and lung cancer; in men, prostate cancer and leukemia show the highest increase of rates (p < 0.01). The consistency of our observations with those of the Ontario group is discussed.

Alzheimer's disease: preliminary study of spatial distribution at birth place.

Alzheimer's disease (AD) is a neurodegenerative disorder which is characterized by a progressive loss of memory and the alteration of cognitive functions. At least three chromosomal segments have been associated with early-onset AD in genetic linkage studies. These results argue for a certain degree of heterogeneity in the genetic origin of some forms of AD, although environmental risk factors cannot be ruled out in late-onset AD. In this preliminary study, we analyzed the geographical distribution of the birth places of a sample of 235 AD cases born in a defined region of Quebec (Canada), between 1895 and 1935. We wished to test the hypothesis that risk factors acting at, or around birth place and time play a role in the etiology of AD. The field of study was divided into rural and urban areas. A reference population of live births was used to compute a measure of odds ratio (OR). The OR results showed a statistically significant excess of AD cases in the rural area as compared to the reference population. When stratified for sex, the OR results showed a global excess of female AD cases in both the rural and the urban areas. For men, only the urban area presented a statistically significant deficit. We also analyzed the structures of the genealogical kinships of the rural and urban sub-groups. Although AD cases from the rural sub-group were more closely related to each other than those from the urban one, removal of the kin pairs from the OR analysis seemed to have little effect on the rural/urban distribution of cases. Therefore, the OR results would not appear to be due primarily to a difference in the kinship structures of the two sub-groups. This could mean that some risk factors for AD afflict women more strongly than men, the effect being different depending on the urban or rural origin. However, potential biases such as a higher rate of report for women, differential migration between birth places or a differential mortality ratio between sexes could produce spurious results in the direction of what we have observed in this preliminary study.

Neurodegenerative diseases and risk factors: a literature review.

Degenerative diseases of the central nervous system are significant causes of mortality among elderly people in industrialized countries. For the most part, the causes of these diseases are unknown. It is also very difficult to diagnose this type of disease quickly and accurately. This article reviews the epidemiological research on the principal neurodegenerative disorders, focusing on geographical, hereditary and viral and toxicological exposure correlates. We look in particular at the effect of exposure to toxins as well as the effect that deficiencies of elements such as calcium and selenium could have on the development of these neurological diseases. We also consider the possible protectionist effect of some variables on the development of certain neurological diseases.

[Preliminary results on the residence distribution at birth of patients with Alzheimer's disease in the Saguenay-Lac-Saint-Jean/Quebec (the IMAGE project)]. / Résultats préliminaires sur la répartition lors de la naissance de sujets atteints de la maladie d'Alzheimer au Saguenay-Lac-St-Jean/Québec (projet IMAGE).

The IMAGE Project is pursuing the establishment of a population-based registry of Alzheimer's disease (AD) cases in the Saguenay-Lac-Saint-Jean (SLSJ) (Quebec). The authors report on the spatial distribution at birth of 221 possible, probable and definite cases. A large network of key-informants for screening AD cases has been established over SLSJ. The spatial distribution of cases at birth and at the onset of disease has been computed by calculating the Alzheimer birth rate (ABR) on the basis of three scales: six specific geographical spheres of screening, all municipalities, and the public health departments. The statistical significance of results was determined using the theoretical Poisson and the Chi square distributions. ABR for each of the geographical spheres of screening showed no statistically significant differences considering either residence at the onset of the disease or residence at birth. Furthermore, differences were observed between rural and urban areas with an interesting trend for a higher number of cases than expected in one area of SLSJ. The spatial distribution of cases considered on the basis of residence at birth appears to show a different pattern, but no significant, from that measured on the basis of residence at the onset of disease. Screening of cases is actively being pursued all across SLSJ by the IMAGE network. There is a clear trend towards rural residence at birth of cases. It remains to see whether or not this observation is due to a geographical concentration of familial cases.