Search PubMed⌕ Search

Biomedical subjects

R G Stevens

Publications and source records attributed to R G Stevens.

68 records · Page 4Linked to original sources
PubMed1984

A cohort analysis of lung cancer and smoking in British males.

Lung cancer mortality in England and Wales among males in the age group 25 to 84 over the years 1941 to 1975 was analyzed. Using cigarette consumption information from the Tobacco Research Council and a statistical model, relative and attributable risks were estimated. The lung cancer deaths could be partitioned into deaths among smokers and deaths among nonsmokers; 88% of total male deaths during the study period could be attributed to smoking. Whereas the mortality rate among smokers increased over the entire span of the analysis, the rate among nonsmokers rose gradually until 1956-1960 and then declined until 1971-1975. The beginning of the decline was coincident with the implementation of the Clean Air Act of 1956. In order to address possible systematic biases in the smoking data, Monte Carlo simulations were performed.

Adult↗
PubMed1984

Malignant melanoma: dependence of site-specific risk on age.

Age-specific incidence of melanoma of the trunk and of the limbs increases slowly with age, while incidence of melanoma of the face increases rapidly. This observation has led to speculation that cumulative ultraviolet exposure determines risk for the face, while acute exposure affects the trunk and limbs. However, there have been strong secular trends in melanoma of the trunk and limbs, but not in melanoma of the face. Analysis of incidence data from Connecticut and Denmark shows that steadily increasing rates in successive birth cohorts account entirely for these secular trends and for the differences seen among the cross-sectional age curves of the various sites. Thus, incidence data do not support the hypothesis that melanoma of the face and melanoma of the trunk and limbs involve distinct pathogenic mechanisms.

Adult↗
PubMed1984

Which computer?

Explore the source record for details and available documents.

Computers↗
PubMed1983

Iron-binding proteins, hepatitis B virus, and mortality in the Solomon Islands.

The hypothesis that serum levels of ferritin and transferrin are associated with subsequent mortality was tested in a population of Solomon Islanders who had been followed over an 8-12-year period beginning in 1966. A case-control analysis of 105 matched pairs showed that 1966-1970 levels of ferritin were higher and levels of transferrin were lower in Solomon Islanders who had died by 1978 than in matched controls who were alive in 1978. These findings support the hypothesis and, in addition, are consistent with the view that increased iron stores are associated with increased mortality. Among females, the association of ferritin with mortality was more pronounced in chronic carriers of hepatitis B virus than in noncarriers.

Adolescent↗
PubMed1982

Temporal trends in breast cancer.

Time-depth breast cancer mortality data from the United States, England and Wales, Canada, and Japan, and breast cancer incidence data from Connecticut, Denmark, and Osaka, Japan, were analyzed. The temporal trends in mortality have been similar in the populations examined. Risks for individual cohorts decreased until about the cohort of 1900, when they began to increase. This pattern can account for the observed increases in the rates at perimenopausal ages (40-55 years). Although the magnitudes of mortality rates in Japan are about one fifth those in the West, they have been changing over time in much the same way as in the West. Cohort effects in incidence in Connecticut and Denmark also dipped around 1900. In Osaka, cohort effects rose from the cohort of 1901 to the cohort of 1936.

Adult↗
PubMed1981

Smoking and cancers of bladder and pancreas: risks and temporal trends.

Mortality data from carcinomas of the pancreas (1941-75) and bladder (1941-70) in England and Wales were analyzed to study the association between cigarette smoking and these cancers. The analysis revealed that: a) The difference in male and female rates in these cancers is attributable to differences in smoking habits; b) the observed increase in mortality in these diseases is almost entirely due to a dramatic increase among smokers. The mortality rate among nonsmokers increased only slowly for carcinoma of the pancreas and actually fell for carcinoma of the bladder. This analysis, which is based on the total number of deaths in the population, yields estimates of relative risk associated with 20 pack-years of smoking of 1.6 and 3.0 for carcinomas of the pancreas and bladder, respectively. The proportion of deaths from carcinoma of the pancreas attributable to smoking increased from 25% in 1941-45 to 52% in 1971-75 in males and from 2 to 15% in females. The proportion of deaths from carcinoma of the bladder attributable to smoking increased form 53% in 1941-45 to 85% in 1966-70 in males and from 4 to 27% in females.

Adult↗
PubMed1980

Two-stage model for carcinogenesis: Epidemiology of breast cancer in females.

A biologically based two-stage model for carcinogenesis is presented that relates events occurring at the cellular level to epidemiologic features of breast cancer in females. This model, which accommodates the physiologic responses of breast tissue to menarche, menopause, and pregnancy, predicts age-specific incidence curves that are in close quantitative agreement with those observed in six test populations: Connecticut, Denmark, Finland, Slovenia, Iceland, and Osaka, Japan. According to the model, hormones influence the epidemiology of breast cancer in females by their action on the kinetics of growth of nonneoplastic breast tissue. As a consequence, it is argued that hormones are likely to be unimportant in determining overall risk in populations. The protective effect of an early first birth predicted by the model is in good quantitative agreement with data from a multinational study. Other epidemiologic features of breast cancer are logically explained within the framework of the model. No feature of the epidemiology of breast cancer requires that premenopausal and postmenopausal breast cancer be considered distinct entities from the point of view of pathogenesis.

Adolescent↗
PubMed1979

Effect of age on incidence of breast cancer in females.

Incidence and mortality data on breast cancer in females from various Occidental (Western) and Japanese populations were analyzed. After adjustment for birth cohort and year of event, the age curves from all the Western populations were very similar in shape. The age curve for Osaka incidence was very similar in shape to the Western incidence curves. The Osaka curve continued to increase after menopause; the postmenopausal decrease in rates in individual cross sections was the result of a strong cohort effect. The premenopausal mortality curve for Japan was very similar in shape to the Western curves; however, the postmenopausal Japanese mortality curve had a smaller slope at each point.

Adult↗
PubMed1979

The influence of age, year of birth, and date on mortality from malignant melanoma in the populations of England and Wales, Canada, and the white population of the United States.

The age-adjusted death rates from malignant melanoma of the skin have increased from 1951 to 1975 by about 3% per year in the populations of England and Wales, Canada, and the white population of the US. This is due to large increases in risk of successively later born cohorts. Any effects of earlier diagnosis of improved treatment within the period 1951--1975 have been sufficiently steady to fail to alter these trends. The slope of the log rates with log age is about 3.5. Projections of rates for at least the next decade can be made with some confidence, and provide a basis for evaluating control measures.

Adult↗
PubMed1979

Estimation of relative risk from vital data: smoking and cancers of the lung and bladder.

Mortality data from cancers of the lung and bladder in England and Wales were analyzed. With the use of detailed information on cigarette consumption, a nonlinear least-squares analysis showed that the differences between males and females in the rates of these cancers could be explained on the basis of differences in smoking habits. Furthermore, estimates of the relative risk due to smoking were obtained. The relative risks of smoking 146,000 cigarettes (equivalent to 20 cigarettes/day for 20 yr) were 4.3 for lung cancer and 2.9 for bladder cancer. These estimates agree with those obtained by other types of epidemiologic studies.

Adult↗
PubMed1978

Tuberculosis: generation effects and chemotherapy.

Mortality from pulmonary tuberculosis in the United States was analyzed by cohort. The introduction of effective chemotherapy necessarily renders models based on generation differences alone inappropriate in this disease. However, such models continue to be used. The data show major departures from the prediction of a generation based model during the 1950's. Projection of the 1941 rates and cohort slopes to 1970 using a generation model predicts 358,000 more deaths than were actually certified. The departure was smaller for blacks than for whites, and differences in delivery of treatment probably account for this. Projections of mortality need to be made for the planning of control measures. However, such projections must be done with the understanding that inter-cohort differences can be altered during adult life.

Adolescent↗