Cigarette smoking and the risk of colorectal cancer in women

Colorectal cancer incidence rates for smokers, nonsmokers living with smokers (i.e., passive smokers), and nonsmokers in smoke-free households were compared in a 12-year prospective study of 25,369 women who participated in a private census conducted in Washington County, MD, in 1963. Women who smoked had a decreased relative risk of colorectal cancer compared with the risk for nonsmokers (age-adjusted relative risk, 0.76; 95% confidence interval, 0.52-1.10). The risk for passive smokers was similar to that for smokers. The relative risks were significantly reduced for older women; relative risks were 0.42 for smokers and 0.66 for passive smokers over age 65. The data suggest that older women who smoke have a lower risk of colorectal cancer than nonsmokers. The effect may be mediated by an antiestrogenic effect of smoking.

Radon-222 concentration in groundwater and cancer mortality in North Carolina

In a geographic correlation study, we explored the possibility that residential exposure to radon in groundwater may be related to cancers other than lung cancer. Measurements of radon in groundwater and 1978-1982 cancer mortality data from North Carolina, USA were used to investigate this relationship. Counties were categorized in two levels of radon exposure according to measured radon concentration and geology. In the lower exposure group (unexposed) county mean radon concentrations ranged from 0-228 pCi/l (0-8436 Bq/m3), and in the upper group (potentially exposed) the range of county average concentrations was 229-10892 pCi/l (8473-403004 Bq/m3) (median 1375 pCi/l (50875 Bq/m3)). Adjusted mortality ratios and 95% confidence intervals were calculated for selected cancers, including leukemias, gastro-intestinal tract cancers, and respiratory tract cancers excluding lung cancer. In contrast to other ecologic studies, we found no consistent association between radon level and cancer mortality.

Using father's age to explore the role of germ cell mutation as a cause of human cancer

It has been conjectured that single-gene mutations in the human sperm or egg may increase the risk of cancer in subsequent offspring. We propose an epidemiological test of this hypothesis, using an observation from paediatric genetics. Children with autosomal dominant disease are occasionally born into previously unaffected families. This signals the probable mutation of a parent's germ cell. Risk of producing these offspring is found to be related to father's age but not to mother's age. This suggests that sex differences in germ cell production lead to a greater accumulation of germ cell mutations in men than women. If germ cell mutations increase with father's age, and if germ cell mutations are associated with subsequent increase in cancer risk, then some association should exist between age of the father (but not the mother) and risk of cancer. We discuss the few available data, and suggest ways that this hypothesis might easily be tested.

Heart disease mortality in nonsmokers living with smokers

A private census of Washington County, Maryland, in 1963 obtained information on smoking habits of all adults in the census, and death certificates of all residents who died in the next 12 years were coded for underlying cause of death and matched to the census. Among the white population aged 25 and over, 4,162 men and 14,873 women had never smoked. In this group, death rates from arteriosclerotic heart disease were significantly higher among men (relative risk (RR) = 1.31, 95% confidence interval (CI) 1.1-1.6) and women (RR = 1.24, 95% CI 1.1-1.4) who lived with smokers in 1963, after adjustment for age, marital status, years of schooling, and quality of housing. Among women, the relative risk increased significantly (p less than 0.005) with increasing level of exposure; among men, there was little evidence of a dose-response relation. The relative risks for nonsmokers who lived with smokers were greatest among both men and women who were younger than age 45 in 1963, but the number of deaths in these groups was small, and confidence intervals were broad. These results suggest a small but measurable risk for arteriosclerotic heart disease among nonsmokers who live with smokers.

Epidemiology of acute myelogenous leukemia

The epidemiologic literature suggests that environmental exposures, familial susceptibility, and cytogenetic changes affect AML risk in childhood and adulthood. Unfortunately, many studies are limited by inadequate sample sizes, imprecise case definition, or inadequate exposure measurement. Few studies have singled out AML alone, either because of insufficient numbers or because methods of case ascertainment made it difficult to distinguish specific cell types. Studies of total leukemia or all acute leukemias offer insights into potential risk factors for AML, but may also be misleading in instances when few AML patients were actually included. Future studies should include adequate numbers of patients with AML. At the same time, further refinement of case definition through parameters such as specific cytogenetic changes may make risk factor identification in epidemiologic studies more likely.

Quality of data on parents' smoking and drinking provided by adult offspring

Evaluation of adult health risks from exposures that occurred in childhood may require case-control studies in which subjects who are now adults are asked to provide information that might be more accurately provided by their parents. The quality of parental smoking and drinking histories provided by adult offspring was evaluated in a North Carolina study of cancer risk from childhood exposure to cigarette smoke. A total of 1,036 adult subjects aged 15-59 years were asked about parents' smoking and drinking habits during the subject's childhood and prior to the subject's birth. Parents or siblings of 70% of the study subjects were also interviewed to obtain the same information. Subjects were generally able to provide information on parents' smoking habits, although they were less able to answer questions requiring knowledge of dates or amounts. Accuracy of information provided, as measured by agreement between subjects and mothers or between subjects and siblings, was also good for many simple exposure questions. Age and race influenced the proportion of subjects able to provide information but did not affect the quality of data. Case-control status and habits of parents had an effect on agreement between subjects and mothers for some questions but had no overall effect on the quality or interpretation of data. Cigar smoking and alcohol consumption were not reported as completely or accurately as cigarette smoking. Overall, this study demonstrated the feasibility of evaluating effects of some childhood exposures by obtaining exposure information from individuals who are now adults. Data from such studies can be used to distinguish exposed from nonexposed subjects but cannot readily be used to estimate level of exposure.

Cancer risk in adulthood from early life exposure to parents' smoking

We obtained data on smoking by parents from 438 cancer cases and 470 controls to investigate whether cancer risk in adult life is related to transplacental or childhood exposure to cigarette smoke. Cancer cases were between ages 15 and 59 at time of diagnosis. All sites but basal cell cancer of the skin were included. Cancer risk was increased 50 per cent among offspring of men who smoked. Increased risk associated with father's smoking was not explained by demographic factors, social class, or individual smoking habits, and was not limited to known smoking related sites. Relative risk (RR) estimates associated with father's smoking tended to be greatest for smokers, males, and non-Whites. There was only a slight increase in overall cancer risk associated with maternal smoking. Mother's and father's smoking were both associated with risk for hematopoietic cancers, and a dose-response relationship was seen. The RR for hematopoietic cancers increased from 1.7 when one parent smoked to 4.6 when both parents smoked. Although they should be considered tentative, study findings suggest a long-term hazard from transplacental or childhood passive exposure to cigarette smoke.

Cumulative effects of lifetime passive smoking on cancer risk

Cancer risk from cumulative household exposure to cigarette smoke was evaluated in a case-control study. Overall cancer risk rose steadily and significantly with each additional household member who smoked over an individual's lifetime. Cancer risk was also greater for individuals with exposures during both childhood and adulthood than for individuals with exposures during only one period. These trends were observed for both smoking-related and other sites. These findings are preliminary and must be confirmed with other studies. Nonetheless, they suggest that effects of exposure to the cigarette smoking of others may be greater than has been previously suspected.

Passive smoking in adulthood and cancer risk

Overall cancer risk from adult passive smoking has been examined using smoking by spouse as the measure of exposure. Information on smoking by spouse was obtained for 518 cancer cases and 518 noncancer controls. Cancer cases were identified from a hospital-based tumor registry in North Carolina. Cases included all sites except basal cell cancer of the skin and were between the ages of 15 and 59 years at the time of diagnosis. Cancer risk among individuals ever married to smokers was 1.6 times that among those never married to smokers (p less than 0.01). This increased risk was not explained by confounding by individual smoking habits, demographic characteristics, or social class. Elevated risks were seen for several specific cancer sites and were not limited to lung cancer or other "smoking-related" tumors. Risks from passive smoking appeared greater among groups generally at lower cancer risk (females, nonsmokers, and individuals younger than age 50 years), but were not limited to these groups.

Age at menarche and subsequent reproductive events

A woman's age at menarche may be related to later reproductive performance, including age at first birth and risk of spontaneous abortion. This paper presents data from 2062 women with 4477 pregnancies in the Menstrual and Reproductive Health Study, a prospective study which has been in progress since 1935. Age at menarche is directly related to the age at which a woman marries and conceive a first child, but is unrelated to total fertility, frequency of induced abortion, or risk of stillbirth. Women with either early or late menarche are significantly more likely to have had an ectopic pregnancy. Overall spontaneous abortion risk declines slightly with increasing age at menarche. This trend is not seen, however, when first pregnancies alone are considered. This suggests that the overall trend with age at menarche is not related to a woman's underlying spontaneous abortion risk but rather to unknown selective factors. Women who were very young (less than 11 years) at menarche differ from the others with regard to many measures of reproductive performance. However, these women represent only a small proportion of the total study group.

Cost effectiveness of postoperative carcinoembryonic antigen monitoring in colorectal cancer

Serial monitoring of carcinoembryonic antigen (CEA) has been thought to provide early indication of recurrent cancer in individuals who have undergone curative resection. The current study was designed to assess the costs associated with CEA monitoring. Costs included CEA determinations, other evaluative tests prompted by abnormal CEA values and hospital/surgical costs in patients undergoing "second-look" procedures. The authors estimated that the cost per resectable tumor was $24,779; but, under optimal circumstances, it might be as low as $10,446. The most important factors were the percentage of recurrent tumors and the proportion of these that were resectable. It proved slightly more efficient to limit the preoperative workup rather than to decrease the frequency of CEA determinations. The true benefits of CEA initiated second-look surgery in terms of prolonged survival remain unknown. More clinical experience is needed to better understand these benefits.

Radiation-induced cancers of the colon and rectum: assessing the risk

Individuals who have received pelvic irradiation are reported to be at increased risk to develop subsequent malignancies in the large bowel. In order to plan appropriate follow-up for these patients, it is necessary to understand the magnitude of their risk. In this paper we review the literature on colorectal cancer after irradiation and estimate the excess risk based upon available data. Women who are irradiated for gynecologic cancer may have a relative risk for subsequent colorectal cancer of 2.0-3.6 based on best estimates. This risk is calculated independent of any risk imposed by underlying disease. These women are appropriate targets for careful surveillance for colorectal cancer.

Primary liver cancer mortality in the United States

We analyzed time trends and regional differences in mortality from primary liver cancer in the United States in order to explore possible effects of several factors which have been suggested as causes for liver cancer. Age-adjusted liver cancer death rates have been stable over time except for nonwhite males among whom there has been a 45% increase in liver cancer mortality between 1958 and 1975. The rates for nonwhite males are twice those for white males, and geographic trends in liver cancer mortality differ by race. The rates for white males are greatest in two southern regions, whereas rates for nonwhite males in these same regions are lower than they are elsewhere. Cirrhosis mortality trends parallel those for liver cancer among nonwhite males but not among white males. The similarities in trends for cirrhosis and liver cancer mortality among nonwhite males suggest that cirrhosis may be a major risk factor in this group. For white males, we must look to some other factor to explain the geographic differences that were observed.

Lung cancer and occupation in Alameda County: a death certificate case-control study

A case-control comparison of lung cancer deaths versus deaths from all other cancers occurring in Alameda County, California, between 1958 and 1962 was conducted to investigate possible associations between lung cancer and occupation. Age-adjusted, sex-specific analyses indicated that a history of work in certain industries and occupations was associated with an increased risk of lung cancer. Among males, a significant positive association was found for glass, metal, furniture, professional and photographic equipment, rubber, leather and plastic manufacturing; water and air transportation; auto repair services; and construction. Specific occupations associated with a significant positive risk for males were: electricians, aircraft mechanics, painters, plasterers, machine operators, construction workers, bus and truck drivers, and guards and nightwatchmen. Among females, beauticians had a significantly high risk associated with lung cancer. These results were consistent with other studies of lung cancer related to occupation.

Neoplasms following childhood radium irradiation of the nasopharynx

Eighteen to 35 years after admission to a clinic for the prevention of deafness, no increased overall cancer risk could be detected among 904 persons who had been treated with nasopharyngeal radium irradiation when compared with the risk among 2,021 persons who were either treated surgically or not treated at all, although there were differences at specific sites. An increased risk of developing both benign and malignant head and neck tumors was found among irradiated persons. Whereas no one head and neck site showed a statistically significant excess, a slight excess of brain cancer occurred 15-20 years after radium treatment. No increase in thyroid cancer risk was observed, a result possibly attributable to the low radiation doses to this organ, and the relatively small population irradiated.

Spontaneous abortion over time: comparing occurrence in two cohorts of women a generation apart

A prospective study of menstrual cycles and reproductive outcomes has been in progress since 1935. Data from this study are used to describe the risk of spontaneous abortion in two time periods 26 years apart. Out of the total of 3889 women who have enrolled in this study, two cohorts of women are selected for analysis: cohort one consists of 2070 university students who entered the study in 1935-1944, and cohort two consists of 1375 students a generation later, 1961-1970. Cohort one has contributed 2408 pregnancies, and cohort two, 1493 pregnancies. Overall spontaneous abortion risk for the two cohorts is 16.9% and 13.1%, respectively. However age-specific risks of spontaneous abortion do not differ for the two groups, nor is there a difference in the gestational duration of spontaneously aborted pregnancies.