A case-control study of 374 patients with primary epithelial cancers of the oral cavity, oro- and hypopharynx, and larynx is reported, the controls being patients with selected other cancers, matched for age and sex. Of all eligible patients, 93% were interviewed. Increased risks were seen with alcohol consumption and, less strongly, with smoking, which for all sites could be adequately fitted by either a multiplicative or an additive model. However, the site-specific relationships were different, alcohol consumption being significantly associated only with oral cavity, pharyngeal and extrinsic laryngeal tumours, and smoking only with intrinsic laryngeal tumours. Increased risks were associated with low socio-economic status, the unmarried state, and poor dental care. No significant associations were seen with specific occupational exposures.
The mortality rate (stillbirths and infant deaths) from anencephalus from 1950-1969 in 36 cities of over 50,000 population in Canada showed a negative association (r = -.39) with the concentration of magnesium in water sampled at domestic taps. The mortality rates showed negative associations with mean income and longitude, and a multiple regression model using the three factors showed significant effects of each and accounted for 69% of the intercity variation in rates. There were no significant associations seen with water calcium concentration or total hardness. Income, magnesium and longitude were also negatively associated with mortality rates from spina bifida, hydrocephalus, other congenital abnormalities, and total stillbirth and infant death rates, but the association with magnesium was significant only for total stillbirths. The negative association of anencephalus mortality and magnesium levels was also seen in a sample of 14 smaller towns in Ontario.
A study of all newly incident melanoma patients in British Columbia in 1991-1992 was undertaken to test the hypothesis raised by an earlier study, which showed that in younger patients the incidence rate of melanoma per unit area of skin was higher on intermittently exposed skin areas than on continuously exposed areas. Using 1,033 patients and a more detailed body site categorisation than was previously possible, our results confirmed that in both men and women under age 50 the highest melanoma density was on the back. At ages over 50, the greatest density occurred on fully exposed sites, such as the face, though the dorsum of the hand and forearm, likely also to have high exposure, show very low melanoma densities. Differences between males and females correlate well with differences in likely exposure patterns. These results were seen for all invasive cutaneous melanomas combined; the patterns were similar for subtypes and for both invasive and in situ melanoma, with the exception of lentigo maligna melanoma (LMM), which occurs almost exclusively on the face, even at younger ages. Comparison with the earlier study (1976-1979) shows that the age-standardised rates for melanoma excluding LMM have increased by 60%, with the greatest proportional increase being at younger ages; in the recent data, the age-standardised rate for intermittently exposed sites exceeds that for usually exposed sites. Our results confirm that intermittent sun exposure has a greater potential for producing melanoma than continuous exposure at ages below about 50, though at older ages melanoma is more common on body sites with continuous sun exposure.
We compared age-adjusted mortality rates for cancer of selected sites for Chinese, Japanese, and native Indian residents of British Columbia during the years 1964-73 to the corresponding rates for the white population. Mortality from all cancers of the Chinese did not differ significantly from that of whites. Elevated rates are seen for cancer of the nasopharynx in both sexes, of the liver and esophagus in males, and of the lung in females. Chinese males had a lower mortality than whites from stomach, prostate, and bladder cancer and brain tumors, whereas females had a lower mortality from tumors of the colon, breast, and ovary; both sexes had a lower mortality from leukemia. For Japanese males and females, the mortality rates for all cancers combined were similar to those of the white population. The rates for cancer of the stomach and gallbladder were higher in both sexes; males also showed a higher rate of liver cancer. Prostate and breast cancer mortality rates were lower. Native Indian males had a lower mortality rate from all cancers combined; the difference was significant for stomach, colon, lung, and prostate cancers, and for leukemia. Native Indian females showed a lower rate for ovarian cancer and a higher rate of tumors of the gallbladder and uterine cervix, but their overall cancer mortality was similar to that of whites.