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Biomedical subjects

G R Howe

Publications and source records attributed to G R Howe.

At least 145 records · Page 8Linked to original sources
PubMed1981

Tobacco, alcohol, asbestos, and nickel in the etiology of cancer of the larynx: a case-control study.

A case-control study of laryngeal cancer was conducted in southern Ontario between 1977 and 1979 with 204 subjects with newly diagnosed cancer and 204 controls, individually matched by sex, age, and residence. Tobacco products and alcohol showed strong associations with cancer of the larynx for males, with relative risks (RR) for users of cigarettes, cigars or cigarillos, pipes, and alcohol of 6.1, 2.9, 1.6, and 5.2, respectively. The population attributable risk percent for males using tobacco products and alcohol together was estimated to be 94%. Cigarette smoking was also an important risk factor for females, although the small number of female pairs (20) precluded any meaningful detailed analysis of other possible risk factors. The RR for males for exposure to asbestos after the effects of cigarette smoking were controlled was 2.3, and the effects seemed restricted to cigarette smokers. The findings on asbestos were based on small numbers of cases and controls exposed and consequently were subject to large sampling errors. The estimate was consistent, however, with that from other studies and supported a causal role for asbestos exposure and cancer of the larynx. The RR for males for exposure to nickel was 0.9.

Asbestos↗
PubMed1981

Some methodological issues in epidemiological studies of fat and cancer.

Three types of approach to the study of the possible relationship between fat and cancer are discussed, namely, correlational, case-control, and cohort studies. The advantages and limitations of each method are analyzed, and it is emphasized that a necessary prerequisite to direct observational studies in humans is the development of a satisfactory and uniform method of a diet assessment. Despite the problems, epidemiological research in this area offers considerable potential for cancer prevention.

Colonic Neoplasms↗
PubMed1980

A case-control study of diet and colo-rectal cancer.

A case-control study of cancer of the colon and rectum has been conducted in Calgary, Alberta and Toronto, Ontario, Canada. A total of 348 cases of cancer of the colon and 194 cases of cancer of the rectum were individually matched by age, sex and neighbourhood of residence to 542 population controls and frequency match to 535 hospital controls who had undergone an abdominal operation. Each subject received a personal medical history questionnaire and a quantitative diet history questionnaire. Data on a number of potential non-nutrient risk factors for bowel cancer and on the consumption of 9 nutrients in the 2-month period up to 6 months before interview were analysed. The dietary data thus refer to recent diet consumed in a period antedating the diagnosis of, and in most cases symptoms from, large-bowel cancer in the cases, and a corresponding time period in the controls. The major findings were an elevated risk for those with a history of bowel polyps, and for those with an elevated intake of calories, total fat, total protein, saturated fat, oleic acid and cholesterol. No association was seen with an elevated intake of crude fibre, Vitamin C and linoleic acid. The nutrients for which an increased risk was demonstrated were highly correlated, though multivariate analysis using logistic regression indicated highest risk for saturated fat, with evidence of a dose-response relationship. The findings in both cancer sites, both sexes and with both sets of controls were quantitatively very similar. The population-attributable risk for colon and rectal cancer combined was estimated from the neighbourhood controls to be 41% for males and 44% for females for saturated fat intake and 9.8% and 6.4% respectively for any history of polyps.

Adult↗
PubMed1980

Fertility regulation in male rats and hamsters with alkylating agents.

A single intratesticular injection of TEPA or Thio-TEPA induced a period of infertility lasting 1-2 months. Restoration of fertility was characterized by a reduction of the litter size resulting from the first inpregnation post-treatment. There was no evidence of tissue pathogenesis 6-12 months after treatment.

Animals↗
PubMed1980

Evaluation of a diet history questionnaire for epidemiologic studies.

This study was conducted to evaluate a detailed diet history questionnaire. Diet histories obtained from 16 men were compared with food records kept by their partners for a 30-day period. Mean estimates for all 13 nutrients calculated were higher with the diet history than with food records. Positive correlation coefficients were found between estimates from the two methods for all nutrients as well as food groups and six of the 13 nutrients gave a good fit for the corresponding regression equations. The questionnaire was also evaluated by repeating it after six months on 26 case-control pairs of an ongoing diet and cancer study. High correlation coefficients were obtained for most nutrients for the controls. However, cases showed lower correlations probably due to changes in their diet. The study found that the diet history method as an estimate of dietary patterns among groups shows sufficient validity and reliability to make it a useful instrument for epidemiologic studies.

Adult↗
PubMed1980

Tobacco use, occupation, coffee, various nutrients, and bladder cancer.

In a Canadian population-based case-control study of 480 males and 152 female case-control pairs, the relative risk for development of bladder cancer for ever used versus never used cigarettes was 3.9 for males and 2.4 for females, with a dose-response relationship in both sexes. A reduced risk was associated with the use of filter cigarettes compared to nonfilter cigarettes. After control for cigarette usage, a significant risk was noted for male pipe smokers. For male ex-smokers the risk after 15 years of no smoking was less than one-half that of current male smokers. Bladder cancer risk was found for workers in the chemical, rubber, photographic, petroleum, medical, and food processing industries among males and for workers occupationally exposed to dust or fumes among both sexes. Bladder cancer risk was elevated for males consuming all types of coffee, regular coffee, and instant coffee and for females consuming instant coffee, but no dose-response relationship was found. Risk was found for males consuming water from nonpublic supples but not for females. No risk was observed in males or females consuming nitrate-containing foods, beverages other than coffee, or fiddlehead greens. Hair dye usage in females and phenacetin usage in males and females carried no risk. Divergent findings by area for aspirin suggested that an overall association was not causal. Reevaluation of the data on artificial sweeteners confirmed a significant bladder cancer risk in males and a dose-response relationship. The cumulated population attributable risk for bladder cancer was 90% for males from cigarette smoking, industrial exposure, and exposure to nonpublic water supplies and 29% for females from cigarette smoking, industrial exposure, and instant coffee consumption.

Age Factors↗
PubMed1980

Cancer incidence and mortality in relation to occupation in 700,000 members of the Canadian labour force.

The mortality and cancer incidence experience of a 10% sample of the Canadian labour force has been monitored by using computerized record linkage to the Canadian National Mortality and Cancer Incidence Data Bases. Occupation and industry data are available for the sample for the years 1965-1971, and the data are being used both to generate and test hypotheses concerning occupational exposures and increased risk of various cancers. It is planned to continue the monitoring process in future years, and as the number of cancer cases and deaths in the cohort accumulate, the data will provide an increasingly valuable utility for cancer researchers.

Adult↗
PubMed1979

Isoniazid exposure in relation to cancer incidence and mortality in a cohort of tuberculosis patients.

41 226 isoniazid exposed and 22 811 non-exposed patients admitted to Canadian institutions for the treatment of tuberculosis from 1952 to 1960 were followed to 1973 by computerised record linkage to the National Death Index and, for 1969 to 1973, to the National Cancer Incidence Reporting System; The mortality for the total cohort compared to that expected from the mortality in the Canadian population, was greater than expected for tuberculosis, other chest diseases and certain cancer sites associated with cigarette smoking (except bladder cancer). There was, however, no difference between the isoniazid-exposed and non-exposed in mortality from all cancer and individual cancer sites, except for oesophageal cancer in males. Cancer incidence from 1969 to 1973 was also similar for the isoniazid- exposed and non-exposed groups. An elevated standardised incidence ratio was seen only for buccal cavity and pharynx in male exposed subjects. It is concluded that this study provides additional negative evidence on the carcinogenicity of isoniazid in man.

Adolescent↗
PubMed1978

A comparison of dietary methods in epidemiologic studies.

Three methods of estimating group and individual dietary consumption have been developed and assessed in a case-control study of diet and breast cancer. The methods comprised a 24-hour recall, a detailed quantitative diet history directed to the most recent two-month period and the two-month period six months before, and a four-day diet diary. There is a high degree of correlation between the estimates of food consumption for the controls using each of the methods. The highest estimate was obtained from the diet history, with a slightly higher estimate in the period six months before than the current period, while the lowest is found in the 24-hour recall. The latter corresponds with the same method in a Nutrition Canada Survey. It is concluded that all methods ara applicable to case-control studies, but the diet history is preferred when current food intake may be influenced by a disease.

Breast Neoplasms↗
PubMed1978

A study of diet and breast cancer.

A case-control study has been conducted in four areas in Canada in which 400 cases of breast cancer matched by age and marital status with neighborhood controls were administered a medical and dietary history questionnaire, a 24-hour recall for dietary information and a four-day diet record. The Study has produced evidence of an association between an increased intake of nutrients, especially total fat, in both pre-menopausal and post-menopausal women with breast cancer. Reasons why a weak association might have been anticipated are discussed, and it is concluded that in reality the association is stronger. Furthermore, its consistency with other evidence, both experimental and international, suggests that it is causal.

Age Factors↗
PubMed1978

An epidemiologic study of breast cancer.

A case-control study has been conducted in four areas of Canada in which 400 cases of breast cancer matched by age and marital status with neighborhood controls were administered medical and dietary questionnaires. The study is suggestive of an increased risk of breast cancer in post-menopausal women with younger age at menarche and an increased risk with delay of age at natural menopause. No protective effect of early age at first pregnancy was demonstrated in either pre- or post-menopausal women. An increased frequency of pregnancies of four months duration or less was found in cases compared to controls and a greater frequency in pre-menopausal cases compared to controls of a history of irregular menstrual periods. In pre-menopausal women no association has been found between increased height and weight as risk factors for breast cancer. For post-menopausal women, however, a weak association with increased height has been found, while a strong association with increased weight both at the time of menopause and the 12 months preceding diagnosis has ben confirmed.

Adolescent↗