Occupational physical activity and risk for breast cancer in a nationwide cohort study in Sweden.

OBJECTIVE: Our purpose was to investigate effects of physical activity on risk for breast cancer. METHODS: From the Swedish nationwide censuses in 1960 and 1970 we defined three partly overlapping cohorts of women whose occupational titles allowed reproducible classification of physical demands at work in 1960 (n = 704,904), in 1970 (n = 982,270), or with the same demands in both 1960 and 1970 (n = 253,336). The incidence of breast cancer during 1971-89 was ascertained through record linkage to the Swedish Cancer Register. We used Poisson regression to estimate relative risks (RR). RESULTS: A total of 20,419, 22,840, and 8261 breast cancers, respectively, were detected in the three cohorts. In all three cohorts the risk for breast cancer increased monotonically with decreasing level of occupational physical activity and with increasing socioeconomic status. Among women with the same estimated physical activity level in 1960 and 1970 the RR was 1.3 for sedentary as compared with high/very high activity level (95% CI 1.2-1.4; p for trend < 0.001). Adjustment for socioeconomic status virtually eliminated this association (RR 1.1; 95% CI 0.9-1.2; p for trend 0.12) leaving a statistically significant 30% gradient only among women aged 50-59 years at follow-up. The association between socioeconomic status and breast cancer risk was largely unchanged after adjustment for occupational physical activity. CONCLUSION: The protective effect of occupational physical activity on breast cancer risk, if any, appears to be confined to certain age groups.

Vitamin A supplements, fried foods, fat and urothelial cancer. A case-referent study in Stockholm in 1985-87.

In a population-based case-referent study of urothelial cancer in Stockholm during 1985-87, information was obtained from 78% of 418 identified cases and 77% of 511 selected referents. The relative risk (with 95% confidence interval) for intake of vitamin A supplements was 0.5 (0.2-1.0), with a dose-response relationship with increasing frequency of consumption. Increased risks of urothelial cancer were seen for several fried foods, for example fried meat [relative risk 1.4 (1.0-1.8) for weekly intake] and fried potatoes [relative risk 1.6 (1.1-2.6) for weekly intake]. Subjects with a high intake of fried foods, as defined by a collapsed variable, had a relative risk of 2.4 (1.4-4.2). A dose-response relationship was also seen with an increasing average daily intake of fat [relative risk 1.7 (1.0-2.8) in the highest quintile], but adjusting for fried foods decreased the relative risk, and it is uncertain whether the adjustment allowed for residual confounding. No association was noted for meat other than fried, but the analysis was based on small numbers.

Increased risk of urothelial cancer in Stockholm during 1985-87 after exposure to benzene and exhausts.

In a population-based case-referent study of urothelial cancer in Stockholm during 1985-87, information was obtained from 80% of 320 identified male cases and 79% of 363 selected male referents. Industrial exposures were assessed for each subject by an industrial hygienist on the basis of questionnaire data. Exposure to benzene (any annual dose) gave a relative risk (with 95% confidence interval) of 2.0 (1.0-3.8). The highest risk was seen for a high annual dose. Subjects exposed to both diesel and petrol exhausts (moderate/high annual dose) had a relative risk of 7.1 (0.9-58.8). However, adjusting for benzene changed the relative risk to 5.1 (0.6-43.6). It might be rewarding to consider whether benzene from petrol confounds the associations previously suggested between exhausts and urothelial cancer. Exposure to polychlorinated biphenyls (PCB) gave a relative risk of 3.3 (0.6-18.4).

Colorectal cancer in Sweden. A descriptive epidemiologic study.

In a register-based 19-year follow-up we studied the incidence rate of colorectal cancer in the Swedish 1960 census population. A total of 53,377 cases were identified: 28,003 men and 25,374 women. A U-shaped distribution of tumors in the large bowel was observed, with a minimum in the descending colon. Other findings were 1) An incidence gap between elderly men and women increasing with age and with distal direction in the large bowel; 2) An increase in the incidence of colorectal cancer with population density; 3) A higher incidence of colorectal cancer in the southwestern region than in the northern region and 4) A lower incidence of colon cancer among blue than among white collar workers and a lower incidence of colorectal cancer among never married men than among other men.

Physical activity and colon cancer risk.

The association between low physical activity and colon cancer was examined in a Swedish 14-year follow-up study of 16,477 subjects. The relative risk (RR) of colon cancer in subjects with low physical activity was estimated at 3.6 (1.3-9.8, 95% confidence interval). An association was observed for both men and women, and for low physical activity during occupational hours (RR = 1.6, 0.8-2.9) as well as during recreational hours (RR = 1.6, 1.0-2.7). The relative risk for rectal cancer was not elevated. In the study we controlled for age, gender, domicile and, to some extent, for diet. A possible mechanism is that low physical activity could prolong the transit time of the stool in the colon and thereby the duration of contact between the mucosa and fecal carcinogens.

Serum cholesterol and cancer--a retrospective case-control study.

The time relationship between low serum cholesterol and the subsequent development of malignant neoplasms was examined in a case-control study of 100 cases of cancer death and 393 controls. The serum cholesterol levels were followed by repeated blood analysis over a 16-year period. An association between low serum cholesterol and cancer death was found particularly for malignant neoplasms of the large intestine and rectum. This relationship diminished 7-16 years prior to death suggesting that the low serum cholesterol levels were an effect of the cancer in an early stage and not vice versa.

Sedentary jobs and colon cancer.

The association between physical job activity and colon cancer was examined in a 19-year follow-up study of 1.1 million Swedish men. The relative risk (RR) of colon cancer in men employed in sedentary occupations was estimated at 1.3 (1.2-1.5, 90% confidence interval), with the highest risk for the transverse colon including flexures (RR = 1.6) and the lowest risk for the sigmoid (RR = 1.2). The relative risk for rectal cancer was not elevated. Age, population density, and social class did not confound the relative risk and were controlled for, whereas marital status and geographic region did not. Furthermore, food habits and physical activity during leisure time were examined in the same occupations in another sample and it was judged unlikely that confounding from these factors could explain the association.

Respiratory cancers in furniture workers.

In a 19 year follow up study of 8141 furniture workers nasal adenocarcinoma was 63 X 4 times more common than expected. The findings also indicate an excess risk of adenocarcinoma of the maxillary sinus. No increase in risk was found for laryngeal cancer, lung cancer, or sinonasal cancers other than adenocarcinoma.