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That cigarette smoking is causally associated with development of cardiovascular disease is recognized unequivocally. Epidemiological studies worldwide have documented the many pathways of influence and synergism by which this ubiquitous but artificial habit exerts its ill effects on cardiorespiratory and other body systems, leading not only to cardiovascular disease but to cancer and other ailments. Current investigations among college alumni, women, elderly, and other subgroups provide data on how various independent influences combine with smoking to establish risk and promote pathogenesis of cardiovascular disease. Their findings also confirm that cigarette smoking is one of the strongest instigators. All of this knowledge has implications for the design and implementation of effective intervention programmes.

Much important information about the cardiovascular benefits and hazards of exercise requires the methods of epidemiology, i.e., the study in human populations of frequencies and distributions of disease in terms of time, place, and personal characteristics. The key techniques are comparison and contrast, but epidemiological analyses of physical activity and cardiovascular health often must rely on circumstantial evidence to assess cause-and-effect relationships. The study procedures must be designed to meet rigorous epidemiological principles: statistical association, temporal sequence, consistency, persistence, independence, dose-response relationship, specificity, alterability, repeatability, and confirmation of findings. Through measurement and contrast, study procedures aim to determine whether physically active persons experience a lower incidence of cardiovascular disease than do persons more sedentary. Based on these principles, current evidence indicates that exercise induces protective benefits against coronary heart disease that enable most persons to approach their potential longevity.

This report summarizes the proceedings and recommendations of a National Heart, Lung, and Blood Institute conference on assessment methods for physical activity and physical fitness in population studies held in Bethesda, Maryland, in May, 1984. Synopses of each contributor's presentation are given, as well as specific recommendations for further research. Key areas for investigation were noted as validation and standardization of questionnaires, increased use of activity monitors in exercise research, development of simpler fitness tests, and research into possible surrogate measures for fitness evaluation.

A case-control study of 452 breast cancer patients, aged less than 50 years, and 872 age-, race-, and religion-matched control patients generated relative risk estimates of breast cancer associated with oral contraceptive practices. The relative risk of breast cancer from ever-use of oral contraceptives was 1.1, not significant. Relative risks did not differ by age, interval since first use, interval since last use, or time periods in which steroid compounds differed in composition and potency. However, the relative risks of breast cancer from current use, from 2 to 4 years of ever-use, from 6 or more years of use by women with prior benign breast disease, and from use before first childbirth were increased significantly. The findings suggest the malignant process may be quickened if transformed cells are present during oral contraceptive use. Yet, the findings neither indicate that oral contraception induces breast cancer nor do they exonerate female steroid hormones. The findings do encourage continued surveillance of steroid contraception for cancer induction or promotion. In addition to duration of oral contraceptive use and other measures of dose response, future observations should pay especial attention to use by women before first childbirth and by women with already established benign breast disease.

Rationale and plans are described for a collaborative case-control study of large bowel cancer among Chinese-Americans in Los Angeles and the San Francisco Bay Area and among Chinese in Zhejiang Province, People's Republic of China. A common protocol and questionnaire will be used during personal interviews of approximately 400 Chinese and 300 Chinese-American patients with histologically confirmed adenocarcinoma of the colon or rectum and 2,100 Chinese and Chinese-American controls. Controls will be matched to patients on age, sex, and community of residence. The information requested from subjects will permit testing of hypotheses relating colorectal cancer risk to: dietary factors, including intake of fat (saturated and unsaturated), animal protein, fiber, and vitamins A and E and ascorbic acid; physical activity levels and body mass index; reproductive factors among women; history of bowel disease; and family history of cancer. The information requested of Chinese-American subjects will also permit testing of hypotheses relating cancer risk to such migrant factors as United States versus Chinese nativity, duration of residence in the United States, and Chinese province of ancestry. These factors will be tested for associations with cancers of the colon and rectum separately and with cancers of the large intestine as a whole. We will examine sex and geographic differences in relative risks for etiologic factors, location of tumors within the large bowel, histologic subtype of adenocarcinoma, and frequency of accompanying polyps.

Relationships between ovarian cancer and ability to conceive were explored in a case-control study of 188 women with histologically confirmed epithelial ovarian cancer and 539 control women in the San Francisco Bay Area. Control women consisted of two groups: those hospitalized without cancer, matched to cases by age, race, and hospital of diagnosis (n = 280); and those selected from the general population by random digital dialing, matched to cases by age, race, and telephone prefix (n = 259). Ovarian cancer risk among nulliparous (but not parous) women was positively associated with a history of unsuccessful attempts to conceive, of physician-diagnosed infertility, and of doubts about ability to conceive. Among all women, risk increased with increasing years of unprotected intercourse (P value for trend = 0.02). Risk among women having 10 or more yr of unprotected intercourse was 1.8 relative to that among women having less than 2 such yr (P = 0.01). This association was independent of parity, oral contraceptive use, and estimated years of ovulation, each associated with ovarian cancer. Further, duration of unprotected intercourse combined multiplicatively with each of these latter characteristics in increasing ovarian cancer risk. For example, while cancer risk exhibited a 2-fold range from lowest to highest years of unprotected intercourse and a 4-fold range from lowest to highest years of ovulation, risk among women in the highest joint category of these characteristics was 8 times that of women in the lowest category. We believe that some abnormality of ovulation that reduces the likelihood of conception plays a role in epithelial ovarian cancer.