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Biomedical subjects

R G Stevens

Publications and source records attributed to R G Stevens.

At least 19 recordsLinked to original sources
PubMed1996

Childhood brain tumor occurrence in relation to residential power line configurations, electric heating sources, and electric appliance use.

To assess the relation between childhood brain tumor occurrence and exposure to potential sources of residential magnetic fields, a population-based case-control study of incident brain tumors was conducted in the Seattle, Washington, area at the Fred Hutchinson Cancer Research Center from 1989 to 1994 among children younger than age 20 years who were diagnosed from 1984 to 1990. The specific aims were to evaluate whether proximity to high-current residential power lines, as defined by the Wertheimer-Leeper code, or use of electric appliances or electric heating sources by the mother while pregnant or by the child before diagnosis were associated with increased risks of brain tumor occurrence. The mothers of 133 cases and 270 controls (recruited by random digit dialing) participated. Risk of brain tumor occurrence did not increase with increasing exposure, as indicated by the five-level Wertheimer-Leeper code. When exposure was dichotomized as high versus low, the odds ratio was 0.9 (95% confidence interval 0.5-1.5) and did not vary significantly by sex, age, or histology. No elevations in risk were found for ever versus never use of electric blankets, water beds, or electric heating sources. Odds ratios were slightly elevated for nine appliances and were at or below 1.0 for eight others. These data do not support the hypothesis that exposure to magnetic fields from high-current power lines, electric heating sources, or electric appliances is associated with the subsequent occurrence of brain tumors in children.

Adolescent↗
PubMed1995

Childhood cancer occurrence in relation to power line configurations: a study of potential selection bias in case-control studies.

Several case-control studies have reported positive associations between childhood cancer and proximity to high-current residential power lines as defined by the Wertheimer-Leeper code. We conducted a study to evaluate whether or not differential nonparticipation of controls as a function of socioeconomic status is likely to account for the observed associations. We assessed the relation of annual family income to the Wertheimer-Leeper code in a sample of 392 households in western Washington state, and we evaluated the magnitude of bias that could occur from differential participation of low- and high-income eligible controls. Very-high-current configurations were most frequently located among households with self-reported family income of less than +15,000 per year, and very-low-current configurations were most frequently located among those with self-reported family income of more than +45,000 per year. In a hypothetical case-control study in which: (1) it was assumed that there is no true etiologic relation between power line configurations and cancer occurrence, and (2) controls with very low income were less likely to participate than others, observed (biased) odds ratios ranged from 1.03 to 1.24. If these results are applicable to other areas where case-control studies of cancer in relation to power lines have been conducted, they suggest that relatively lower participation among exposed controls (as a function of very low income) is not likely to account for the elevated risks of 1.5- to 3-fold that have been observed in these previous studies.

Adult↗
PubMed1994

Moderate elevation of body iron level and increased risk of cancer occurrence and death.

The purpose of the study was to address the hypothesis that elevated body iron increases the risk of cancer occurrence and death, and to determine the dose response. Subjects were 3,287 men and 5,269 women participating in the first National Health and Nutrition Examination Survey who had a transferrin saturation determination at enrollment (1971-1975), who remained alive and cancer-free for at least 4 years, and who were followed to 1988 for cancer outcome. Among 379 men who developed cancer over the study period, the mean transferrin saturation at enrollment was 32.1% whereas among 2,908 who remained cancer-free it was 30.7%; the difference for mortality was 32.3% among 233 deaths vs. 30.8% among 3,054 men not dying of cancer. The mean differences among women were not significant. The mean differences in TIBC and serum iron among men were consistent with the findings for transferrin saturation, and all 3 differences were stable over time when examined by years since blood test. Men and women were divided into 5 groups on the basis of baseline transferrin saturation: 0 to 30%, 30-40%, 40-50%, 50-60%, and 60% and higher. Nineteen percent of men had a baseline transferrin saturation above 40% (the last 3 groups), whereas only 10 percent of women had transferrin saturation above 40%. For men and women combined, risk of cancer occurrence in each group relative to the first was 1.0, 0.95, 1.16, 1.38 and 1.81; for mortality the relative risks were 1.0, 0.96, 1.22, 1.29 and 1.73. There is evidence, in this cohort, of elevated cancer risk in those with moderately elevated iron level. This pattern was seen in women as well as in men.

Diet↗
PubMed1993

Breast cancer and electric power.

Breast cancer is a leading cause of death among women in industrialized societies. It is far less common in less industrialized nations and the reason for this difference is unclear. One possibility is the distribution and use of electricity which results in two new exposures in the human environment: light-at-night and electromagnetic fields. These can reduce nocturnal melatonin production. Melatonin, in turn, has a protective effect on breast cancer in experimental animals.

Animals↗
PubMed1993

Biologically based epidemiological studies of electric power and cancer.

As societies industrialize, the health profile of the population changes; in general, acute infectious disease declines and chronic disease increases. Use of electricity is a hallmark of the industrialization process, but there has been no suspicion that electricity could increase the risk of cancer. Recently, however, a number of epidemiologic studies have suggested that electromagnetic fields (EMF) may do just that. Although few cancer experiments have been done yet, there are a number of biological effects of EMF reported in the literature that might provide bases for designing cancer experiments and epidemiologic studies. These include effects of EMF on: a) DNA transcription and translation, b) calcium balance in cells, and c) pineal production of melatonin. Alterations in DNA transcription and translation could have pleiotropic effects. Disruption of calcium homeostasis has many implications including oncogene activation, promotional activity via protein kinases and ornithine decarboxylase (ODC), and increasing oxidative stress. Reduction of melatonin suggests a possible increased risk of cancers of hormone-dependent tissues such as breast and prostate. The idea that a cancer-causing agent must either be an initiator or a promoter should be discarded; indeed, the phenomenologic meaning of these two terms has become confused with imputed mechanistic necessity in recent years. Agents that affect division of normal cells or of fully transformed cells can play an important role in clinical cancer development quite apart from initiation or promotion.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1992

Electric power, pineal function, and the risk of breast cancer.

Breast cancer is the leading cause of cancer death in women in the industrialized world, and the rates of breast cancer incidence are rising. Although risk is high in industrialized societies, it is low in nonindustrialized areas. The search for the causes of breast cancer has not yet yielded a convincing explanation for the geographic and temporal patterns in the occurrence of breast cancer. Generation of electric power is a hallmark of industrialization, and two products of electric power, light-at-night (LAN) and electromagnetic fields (EMF), may affect breast cancer risk. Exposure to either LAN or EMF can decrease production of melatonin by the pineal gland. Melatonin, in turn, has been shown to suppress mammary tumorigenesis in experimental animals. Moreover, recent epidemiological findings indicate an increased risk of breast cancer in workers occupationally exposed to EMF. On the basis of these considerations, it is proposed that the use of electrical power accounts, in part, for the higher risks of breast cancer in industrialized societies.

Animals↗
PubMed1992

Ferritin-iron increases killing of Chinese hamster ovary cells by X-irradiation.

Stationary-phase Chinese hamster ovary cells were cultured in medium containing ferritin (approximately 19% iron by weight) added at concentrations ranging from 0 to 128 micrograms/ml. One set of cultures was unirradiated, and another set was exposed to 4.0 Gy of X-ray. Clonogenic cell survival was assessed in each set of cultures. In the absence of added ferritin, 4.0 Gy killed approximately 50% of the cells. In the absence of radiation, ferritin was not toxic at less than 48 micrograms/ml; above 48 micrograms/ml, toxicity increased with concentration. Apoferritin was not toxic at any concentration tested (up to 1000 micrograms/ml). Although 32 micrograms/ml ferritin, reflecting only a 3-6 fold increase in iron concentration over normal serum, was not toxic, it reduced the survival of X-irradiated cells by an additional 75%. These results indicate that a sublethal concentration of ferritin can be a potent radiosensitizer. This suggests the possibility that high body iron stores may increase susceptibility to radiation injury in humans.

Animals↗
PubMed1991

Serum ferritin and stomach cancer risk among a Japanese population.

Using stored serum samples collected during from 1970 to 1972 and/or 1977 to 1979 from a fixed population in Hiroshima and Nagasaki, Japan, serum ferritin, transferrin, and ceruloplasmin levels were determined immunologically for persons in whom stomach (233 cases) or lung cancer (84 cases) subsequently developed as well as for their controls. An elevated stomach cancer risk was associated with low antecedent serum ferritin levels, with more than a threefold excess among those in the lowest compared with the highest ferritin quintile. The risk did not vary with the time between blood collection and stomach cancer onset, remaining high among those with low ferritin levels 5 or more years before cancer diagnosis. Achlorhydria, diagnosed in a sample of the population about 10 years before the 1970-to-1972 blood collection and up to 25 years before cancer, was an independent marker of stomach cancer risk. In combination, low serum ferritin and achlorhydria were associated with a tenfold increase in the subsequent risk. No effect of transferrin or ceruloplasmin, independent of ferritin, was observed in the gastric cancer risk, and the risk of lung cancer was not related to these three serum proteins. These prospective findings indicate that biologic markers of an increased risk of stomach cancer can be detected long before cancer onset.

Achlorhydria↗
PubMed1990

Iron and the risk of cancer.

Four epidemiological studies have been performed that are generally consistent with the hypothesis that increased available body iron stores increase the risk of cancer or of general mortality. In a study based on the First National Health and Nutrition Examination Survey in the United States (NHANES), 232 men who developed cancer over a ten year period had a mean transferrin saturation of 33.1% at least 4 years before diagnosis, whereas 3,113 men who did not develop cancer had a transferrin saturation of 30.7% (p = 0.002). The hypothesis is based on two possible biological mechanisms. First, iron can catalyse the production of oxygen radicals and these may be proximate carcinogens. Second, iron may be a limiting nutrient to the growth and replication of a cancer cell. There are at least five areas of potential research related to iron and cancer based on these biological mechanisms: (1) etiology of cancer, (2) etiology of radiation-induced cancer, (3) prognosis after cancer diagnosis, (4) cancer risk resulting from therapy, and (5) interactions with other biochemical factors. An unexpected finding of the human studies done to date has been a highly significant negative association of serum albumin and long term cancer risk. Serum albumin is lower in smokers and older people, however, the negative association persists after controlling for these factors.

Female↗
PubMed1990

Smoking and serum proteins in atomic-bomb survivors in Japan.

Associations of smoking habit with serum levels of total protein as well as protein fractions were studied in a population consisting of 4,739 atomic-bomb survivors and unexposed control subjects in Hiroshima, Japan who participated in the 1979-1981 period of the Adult Health Study, an ongoing health follow-up program of the Radiation Effects Research Foundation. Smoking was strongly related to serum protein concentration after correction for age, sex, and body mass index. Among current smokers, levels of total protein, beta globulin, and gamma globulin were significantly lower and levels of alpha-1 and alpha-2 globulin were significantly higher, when compared with nonsmokers. For serum albumin levels a decrease was also noted, but it failed to attain statistical significance. Ex-smokers were indistinguishable from nonsmokers in terms of the serum protein levels analyzed. With an increase of the amount of daily cigarette consumption, monotonic increases of serum levels were observed only in alpha-1 globulin. Duration of smoking was related to increased alpha-1 and alpha-2 globulin. Smoking duration was also associated with albumin level, but the trend was not monotonic. The radiation exposure effect on serum protein level was significant in several instances but was in general much smaller than the smoking effect, and its inclusion in the regression models did not noticeably affect the association between smoking and serum proteins.

Aged↗
PubMed1990

A case-cohort study of lung cancer, ionizing radiation, and tobacco smoking among males at the Hanford Site.

Results of several epidemiological studies of workers exposed occupationally to low levels of radiation have been reported but have not included data on smoking. The authors conducted a case-cohort study of male workers at the Hanford Site with an objective of investigating the association between lung-cancer risk and occupational radiation exposure with appropriate adjustment for tobacco use. Eighty-six lung-cancer deaths for the period 1965-1980 and a stratified random sample of 445 subcohort members were included in the study. Tobacco-use data were obtained from medical records collected over each subject's period of employment. Data from this study were analyzed using methods that took into account both the case-cohort design and changes over time in the quality of the tobacco-use data collected. Tobacco use was not strongly related to the level of radiation exposure, and adjustment for tobacco use did not greatly modify results of analyses assessing the association between lung-cancer risk and cumulative dose equivalent. With or without adjustment for tobacco use, the estimated risks per unit of cumulative dose equivalent were negative, but the 95% confidence intervals were wide and included values several times those estimated from populations with high levels of irradiation.

Cohort Studies↗
PubMed1990

Iron, radiation, and cancer.

Increased iron content of cells and tissue may increase the risk of cancer. In particular, high available iron status may increase the risk of a radiation-induced cancer. There are two possible mechanisms for this effect: iron can catalyze the production of oxygen radicals, and it may be a limiting nutrient to the growth and development of a transformed cell in vivo. Given the high available iron content of the western diet and the fact that the world is changing to the western model, it is important to determine if high iron increases the risk of cancer.

Animals↗