Epidemiology

Occupational exposures and gastric cancer.

Parent ME. Siemiatycki J. Fritschi L.
Epidemiology and Biostatistics Unit, Institut Armand-Frappier, Universite du Quebec, Laval, Canada.
The role of occupational substances as stomach carcinogens has not been well investigated. In 1979, a population-based case-control study was undertaken in Montreal to explore the possible association between hundreds of occupational circumstances and several cancer sites, including the stomach. In total, 250 male patients with pathologically confirmed stomach cancer, 2,289 male controls with cancers at other sites, and 533 population-based male controls were interviewed to obtain detailed job histories and relevant data on potential confounders. Job histories were evaluated by expert chemists and hygienists and translated into a history of occupational exposures. On the basis of results of preliminary analyses and literature review, we selected 16 occupations and industries and 32 substances for in-depth multivariate analysis using the pooled group of cancer and population controls. We found elevated risks for excavators and pavers, forestry workers, electric and electronic workers, motor transport workers, and food industry employees. The substances that were most plausibly associated with gastric cancer were: crystalline silica, leaded gasoline, grain dust, lead dust, zinc dust, hydraulic fluids, and glycol ethers. The paucity of data documenting the association between most of these occupational circumstances and gastric cancer precludes drawing firm conclusions.

Drinking water source and chlorination byproducts. II. Risk of colon and rectal cancers.

Hildesheim ME. Cantor KP. Lynch CF. Dosemeci M. Lubin J. Alavanja M. Craun G.
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892, USA.
We evaluated the association between chlorination byproducts and colon and rectal cancer risk in a population-based case-control study conducted in Iowa in 1986-1989. Data were gathered from 685 colon cancer cases, 655 rectal cancer cases, and 2,434 controls. We calculated odds ratios for the 560 colon cancer cases, 537 rectal cancer cases, and 1,983 controls for whom water exposure information was available for at least 70% of their lifetime. We estimated exposure to chlorination byproducts with two types of measures: duration of lifetime at residences served by chlorinated water and estimated lifetime trihalomethane exposure. For rectal cancer, we observed an association with duration of chlorinated surface water use, with adjusted odds ratios of 1.1, 1.6, 1.6, and 2.6 for 1-19, 20-39, 40-59, and > or =60 years of exposure, compared with no exposure. Rectal cancer risk was also associated with several different measures of estimated lifetime trihalomethane exposure. For colon cancer and subsites, we detected no important increase in risk associated with duration of chlorinated surface water, nor with trihalomethane estimates. When we evaluated chlorination byproducts jointly with other factors, we found larger relative risk estimates for rectal cancer among subjects with low dietary fiber intake. The risk related to > or =40 years of exposure to a chlorinated surface water source was 2.4 (95% confidence interval = 1.5-4.0) for persons with low fiber intake and 0.9 (95% confidence interval = 0.4-1.8) for persons with high fiber intake, relative to the risk of persons with high-fiber diets and no exposure to chlorinated surface water. We observed a similar risk differential for low and high levels of physical activity.

Appendectomy protects against ulcerative colitis.

Year 1998
Derby LE. Jick H.
Boston Collaborative Drug Surveillance Program, Boston University Medical Center, Lexington, MA 02173, USA.
We conducted a case-control study of the protective effect of appendectomy on the development of ulcerative colitis. We calculated the risk of ulcerative colitis in 716 incident cases of ulcerative colitis and 2,747 controls according to appendectomy status, using data from the United Kingdom General Practice Research Database. We also studied a random sample of 100 cases and 100 controls to validate the subject's history of appendectomy. Fifteen cases (2%) and 109 (4%) controls had a computer-recorded history of appendectomy [odds ratio (OR) = 0.5; 95% confidence interval (CI) = 0.3-0.9]. In the sample, the OR was 0.3 (95% CI = 0.1-0.9). Appendectomy appears to protect against ulcerative colitis.

An analysis of the Milwaukee cryptosporidiosis outbreak based on a dynamic model of the infection process.

Year 1998
Eisenberg JN. Seto EY. Colford JM Jr. Olivieri A. Spear RC.
School of Public Health, University of California, Berkeley 94720-7360, USA.
We combined information on the temporal pattern of disease incidence for the 1993 cryptosporidiosis outbreak in Milwaukee with information on oocyst levels to obtain insight into the epidemic process. We constructed a dynamic process model of the epidemic with continuous population compartments using reasonable ranges for the possible distribution of the model parameters. We then explored which combinations of parameters were consistent with the observations. A poor fit of the March 1-22 portion of the time series suggested that a smaller outbreak occurred before the March 23 treatment failure, beginning sometime on or before March 1. This finding suggests that had surveillance systems detected the earlier outbreak, up to 85% of the cases might have been prevented. The same conclusion was obtained independent of the model by transforming the incidence time series data of Mac Kenzie et al. This transformation is based on a background monthly incidence rate for watery diarrhea in the Milwaukee area of 0.5%. Further analysis using the incidence data from the onset of the major outbreak, March 23, through the end of April, resulted in three inferred properties of the infection process: (1) the mean incubation period was likely to have been between 3 and 7 days; (2) there was a necessary concurrent increase in Cryptospordium oocyst influent concentration and a decrease in treatment efficiency of the water; and (3) the variability of the dose-response function in the model did not appreciably affect the simulated outbreaks.

Did Milwaukee experience waterborne cryptosporidiosis before the large documented outbreak in 1993?

Year 1998
Morris RD. Naumova EN. Griffiths JK.
Department of Family Medicine and Community Health, Tufts University Medical School, Boston, MA 02111, USA.
The patterns of incidence and pathways of spread for cryptosporidiosis are poorly understood. In this study, we explored the possibility that drinking water caused significant waterborne cryptosporidiosis in Milwaukee well before the massive documented outbreak in April 1993. We generated time series of daily counts of emergency room visits and hospital admissions for gastroenteritis in Milwaukee using the billing records of the Medical College of Wisconsin for January 1, 1992, through May 3, 1993. The Milwaukee Water Works provided us with data on drinking water turbidity for the same period. The service area of the South Plant experienced a sharp rise in turbidity just before the outbreak. During the outbreak period, gastroenteritis events were most strongly associated with turbidity at a lag of 7 days in children and 8 days in adults. It is reasonable to conclude that these lag times reflect the incubation period of Cryptosporidium. During the 434 days before the outbreak, gastroenteritis events were most strongly associated with turbidity at a lag of 8 days among children and 9 days among adults in the service area of the North Plant, the plant that experienced the highest effluent turbidity during this period. These findings are consistent with the conclusion that waterborne cryptosporidiosis was occurring in Milwaukee for more than a year before the documented outbreak.

Oral contraceptive use and risk of colorectal cancer.

Year 1998
Fernandez E. La Vecchia C. Franceschi S. Braga C. Talamini R. Negri E. Parazzini F.
Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
To evaluate the relation between oral contraceptives and colon and rectal cancer, we analyzed combined data from two case-control studies conducted in six Italian regions between 1985 and 1996. The studies included 803 women with incident colon cancer, 429 with rectal cancer, and 2,793 controls with acute, nonneoplastic, nondigestive, non-hormone-related disorders. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) from unconditional multiple logistic regression equations, including terms for age, center/study period, education, family history of colorectal cancer, menopausal status, age at menopause, parity, use of hormone replacement therapy, body mass index [weight (kg) per height squared (m2)], and total energy intake. Ever-use of oral contraceptives was inversely associated with colon cancer (OR = 0.63; 95% CI = 0.45-0.87) and rectal cancer (OR = 0.66; 95% CI = 0.43-1.01). Duration of use of oral contraceptives was inversely related to risk of colon but not rectal cancer. This study suggests that women who have ever used oral contraceptives are at lower risk of colon and rectal cancer.

Role of different types of vegetables and fruit in the prevention of cancer of the colon, rectum, and breast.

Year 1998
Franceschi S. Parpinel M. La Vecchia C. Favero A. Talamini R. Negri E.
Servizio di Epidemiologia, Centro di Riferimento Oncologico, Aviano (PN), Italy.
We compared the effect of 26 types or groups of vegetables and fruit on the risk of cancer using data from two case-control studies that included 1,225 cases of cancer of the colon, 728 cases of cancer of the rectum, 2,569 cases of cancer of the breast, and 5,155 hospital controls interviewed between 1991 and 1996 in six Italian areas. Most vegetables were inversely associated with cancer of the colon and rectum, whereas only carrots and raw vegetables lowered breast cancer risk. High fruit intake was associated only with a reduction of rectal cancer. Different contents of sugar, fiber, carotenoids, and folic acid in fruits vs vegetables plus the concurrent consumption of oil with vegetables may partly explain these findings.