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Biomedical subjects

M Feychting

Publications and source records attributed to M Feychting.

At least 37 records · Page 2Linked to original sources
PubMed2000

Occupational and residential magnetic field exposure and breast cancer in females.

The purpose of this study was to evaluate the effect of occupational magnetic field exposure on breast cancer in females and to combine residential and occupational magnetic field exposure to reduce misclassification. The study was conducted as a case-control study within a population living within 300 meters of transmission lines in Sweden. We identified cases of breast cancer in females from the national cancer registry, and we selected one matched control per case at random. Residential exposure was estimated through calculations of the magnetic fields generated by power lines. We obtained information about occupation from censuses, and the occupations were linked to a job-exposure matrix that was based on magnetic field measurements. For occupational exposure to magnetic fields over 0.25 microT closest in time before diagnosis, the estimated relative risk was 1.0 [96% confidence interval (CI) = 0.6-1.7]. Women below age 50 years at diagnosis had a relative risk of 1.5 (95% CI = 0.6-3.5). For women below 50 years of age who had estrogen receptor-positive breast cancer, there was a relative risk of 3.2 (95% CI = 0.5-18.9). The results for residential and occupational exposures combined showed similar results.

Biomarkers, Tumor↗
PubMed1999

A Bayesian approach to hazard identification. The case of electromagnetic fields and cancer.

This paper discusses certain issues related to uncertainty in hazard identification. Research on the hypothesis that exposure to 50-60-Hz magnetic and electric fields (EMF) increases the risk of cancer has been ongoing for two decades. Epidemiological studies provide a somewhat consistent pattern indicating an increased risk for childhood leukemia and adult chronic lymphatic leukemia and possibly also for other leukemias and brain cancer. However, there is still no good candidate for a mechanism. Epidemiological studies have throughout the two decades been interpreted with great caution, and final evaluations as to carcinogenicity have been deferred. The reason for this carefulness may be the lack of knowledge about a plausible mechanism. The purpose of this paper is to discuss the process of weighing epidemiological data, experimental data, and other background information into a synthesis such that the evaluation can be based on all data combined. A Bayesian approach to this weighing is discussed along with some alternatives. The Bayesian approach provides a structure for the pooling of evidence and points out where subjective judgments come into play.

Adult↗
PubMed1998

Exposure to motor vehicle exhaust and childhood cancer.

OBJECTIVES: A case-referent study was conducted to test the hypothesis that exposure to motor vehicle exhaust increases the risk of childhood cancer. METHODS: Data from a study of residential magnetic field exposure and childhood cancer were used. From a population of 127000 children living within 300 m of transmission lines in Sweden, 142 cases of childhood cancer were identified, including 39 cases of leukemia and 33 cases of central nervous system tumor. Approximately 4 referents per case were selected at random from the study base. The nitrogen dioxide content of the outdoor air was estimated as an indicator of motor vehicle exhaust. The applied methods give the 99th percentile of the nitrogen dioxide content of the outdoor air for 1-h averages over 1 year. RESULTS: A relative risk estimate of 2.7 [95% confidence interval (95% CI) 0.9-8.5] was found for total cancer at exposure levels of > or = 50 microg/m3, related to those with < or = 39 microg/m3. At > or = 80 microg/m3, the relative risk was estimated at 3.8 (95% CI 1.2-12.1). Elevated, but imprecise risk estimates were found for leukemia and central nervous system tumors. CONCLUSIONS: The results indicate an association between childhood cancer and motor vehicle exhaust, although the number of cases was small. These findings and the results of previous studies suggest that further studies of the association between motor vehicle exhaust and childhood cancer are warranted.

Adolescent↗
PubMed1998

Dementia and occupational exposure to magnetic fields.

OBJECTIVES: The purpose of the present report was to assess whether occupational magnetic field exposure is a risk factor for dementia, in particular for Alzheimer's disease. METHODS: Case-control analyses were applied to 77 dementia cases, 55 of whom had Alzheimer's disease, ascertained from the population-based Swedish twin register. Two reference groups were derived, with 228 and 238 persons, respectively. Occupations were linked to a job-exposure matrix based on magnetic field measurements. Primary occupation, last occupation before reference date, and the occupation with the highest magnetic field exposure during the subject's lifetime were evaluated. RESULTS: For primary occupation, all relative risk estimates were close to unity. For last occupation, at the exposure level > or = 0.2 microT, a relative risk was found for dementia estimated at 3.3 [95% confidence interval (95% CI) 1.3-8.6] and 3.8 (95% CI 1.4-10.2) for reference groups 1 and 2, respectively. The relative risk for Alzheimer's disease was estimated at 2.4 (95% CI 0.8-6.9) and 2.7 (95% CI 0.9-7.8), respectively. For the occupation with the highest magnetic field exposure, the relative risk estimates were close to unity for reference group 1 and slightly elevated for reference group 2. The relative risk estimates were greater for the subjects who were younger at onset (< or =75 years). CONCLUSIONS: These results only partially support previous findings, but they indicate that occupational magnetic field exposure may possibly influence the development of dementia.

Aged↗
PubMed1998

Magnetic fields and breast cancer in Swedish adults residing near high-voltage power lines.

We conducted a case-control study to test the hypothesis that residential magnetic field exposures increase the incidence of breast cancer. The study was based on people who had lived within 300 m of 220- or 400-kV power lines in Sweden at any time between 1960 and 1985. We identified 699 cases of breast cancer in women and 9 cases in men. One matched control per female case and eight per male case were selected at random. Estrogen receptor information was available for a subset of female cases. We assessed magnetic field exposure through calculations of the magnetic fields generated by the power lines before diagnosis. For calculated magnetic field levels > or = 0.2 microtesla (microT) closest in times before diagnosis, we estimated the relative risk to be 1.0 [95% confidence interval (CI) = 0.7-1.5] for women and 2.1 (95% CI = 0.3-14.1) for men. Women younger than 50 years of age at diagnosis had a relative risk of 1.8 (95% CI = 0.7-4.3). For women with estrogen receptor-positive breast cancer, the relative risk was estimated at 1.6 (95% CI = 0.6-4.1), using the exposure cutoff point > or = 0.1 microT. Among estrogen receptor-positive women younger than 50 years at diagnosis, the relative risk increased to 7.4 (95% CI = 1.0-178.1).

Adolescent↗
PubMed1998

Reduced cancer incidence among the blind.

Melatonin is a hormone primarily produced by the pineal gland at night and is suppressed by exposure to light. Experimental studies have indicated that melatonin may protect against cancer development. In the majority of totally blind people, melatonin is never suppressed by light exposure. The aim of this study was to test the hypothesis that blind people have a decreased cancer incidence, and that this effect is more pronounced in the totally blind than in the severely visually impaired. We identified a cohort of 1,567 totally blind and 13,292 severely visually impaired subjects and obtained information about cancer incidence from the Swedish Cancer Registry. We calculated standardized incidence ratios (SIRs) based on the number of person-years and incidence rates specific for national age, sex, and calendar year. Totally blind people had a lower incidence of all cancers combined [SIR = 0.69; 95% confidence interval (CI) = 0.59-0.82]. The risk reduction was observed in both men and women and was equally pronounced in hormone-dependent tumors as in other types of cancer. In the severely visually impaired, SIR was 0.95 (95% CI = 0.91-1.00). The findings support the hypothesis that blind people have a lower cancer incidence, although other explanations than the higher melatonin exposure must also be considered.

Aged↗
PubMed1998

Temporal characteristics of transmission-line loadings in the Swedish childhood cancer study.

A recent study conducted in Sweden reported that 1) leukemia risk in children who lived near 220 or 400 kV electric-power transmission lines was associated with calculated historical magnetic field levels; 2) children living within a distance of 50 m of transmission lines had an elevated risk of leukemia; and 3) there was no association between leukemia and residential magnetic fields measured many years after diagnosis. Subsequently, these investigators found through logistic regression analysis that disease was more strongly associated with calculated historical fields than with distance. Since the calculated historical fields in that study depended predominantly on distance and transmission-line load current, the logistic regression results suggest that historical load current plays an important role in the epidemiological results. Thus, we studied hourly 1974 load-current data for six transmission lines, and we examined 1958-1985 annual load-current data for 112 transmission lines. Most lines exhibited marked diurnal load-current rhythms during 1974, and all six showed systematic weekday-weekend differences. During 1958-1985, average loadings of Swedish 220 and 400 kV lines increased by about 1.3% year. Predictive-value and kappa-statistic analyses indicated that Swedish transmission-line load currents were not stable over long periods, so that contemporaneous load current (or a contemporary magnetic field measurement) was not a good surrogate for historical load current (or historical magnetic fields). The results provide a potential explanation of the failure of the Swedish Study to find an association between leukemia and contemporaneous magnetic field levels measured many years after the etiologic period, and suggest that the inclusion of load-current data could significantly improve the quality of historical field calculations.

Adolescent↗
PubMed1997

Cancer in twins: genetic and nongenetic familial risk factors.

BACKGROUND: Familial clustering has been observed for cancers that occur at specific sites. Most findings, which leave little doubt about the involvement of a heritable (i.e., genetic) component in the development of some cancers, are based on data from "cancer-prone" families or interviews with subjects who have cancer. The study of twins should be of value in cancer epidemiology because twins either are genetically identical or share half of their segregating genes. PURPOSE: We linked the Swedish Twin Registry to the Swedish Cancer Registry, thereby identifying cases of cancer diagnosed from 1959 through 1992 in twins born in the period from 1886 through 1958, to assess the importance of both genetic and nongenetic (i.e., environmental) familial factors in determining cancer risk. METHODS: Same-sex twin pairs with both individuals alive and living in Sweden in 1959-1961 or 1970-1972 were identified in the old cohort (born from 1886 through 1925) or the young cohort (born from 1926 through 1958), respectively, of the Swedish Twin Registry; pairs for whom zygosity (i.e., the number of eggs that gave rise to the twins) could be determined were considered further. The association of cancer with combined genetic and nongenetic familial factors was tested by comparing all twin pairs (regardless of zygosity) in which at least one member of the pair had been diagnosed with cancer at one of several specific sites with pairs in which neither twin had that cancer. Heritable effects alone were tested by comparing monozygotic (one egg) and dizygotic (two eggs) twin pairs. Statistical methods used in quantitative genetics and standard methods for epidemiologic research were used in parallel to analyze the data. RESULTS AND CONCLUSIONS: In the 10503 twin pairs from the old cohort, 361.7 cases of malignant cancer were identified; 918 malignant cancers were identified in the 12883 twin pairs from the young cohort. When cancer sites with a total number of at least 200 cases and at least one twin pair concordant (i.e., both twins affected) for the site were evaluated, namely, cancers of the stomach, colon and rectum, lung, female breast, and prostate, as well as total cancer, profound genetic and/or nongenetic familial effects were identified in twins from the old cohort. Similar findings were obtained for twins in the young cohort for cancers of the prostate and female breast, as well as for total cancer. Genetic and nongenetic familial effects were also identified in twins from both cohorts for in situ cancer of the cervix. The increase in risk of colon and rectum, breast, cervical, and especially prostate cancer, but not stomach or lung cancer, tended to be greater if a monozygotic rather than a dizygotic twin were affected. IMPLICATIONS: The identification of familial effects for total cancer in this study is consistent with the idea that individuals may possess a genetic susceptibility to cancer in general.

Adult↗
PubMed1997

Occupational and residential magnetic field exposure and leukemia and central nervous system tumors.

Studies of magnetic field exposure and cancer have focused on either residential or occupational exposure. We conducted a case-control study taking into account both exposure sources. We identified leukemia and central nervous system tumor cases and controls from a population living within 300 m of transmission lines in Sweden. We have previously reported results considering residential exposure alone. Here, we evaluate the effect of occupational exposure and of the combined exposures. We estimated residential exposure through calculations of the magnetic fields generated by power lines. We obtained information about occupation from censuses and linked the occupations to a job-exposure matrix based on magnetic field measurements. For occupational exposure of > or = 0.2 microT, we estimated the relative risk for leukemia to be 1.7 [95% confidence interval (CI) = 1.1-2.7]. The increased risk was confined to acute myeloid and chronic lymphocytic leukemia. For residential exposure of > or = 0.2 microT, the relative risk for leukemia was estimated at 1.3 (95% CI = 0.8-2.2), with higher risk estimates for acute and chronic myeloid leukemia. We estimated the relative risk for leukemia among subjects highly exposed both at home and at work to be 3.7 (95% CI = 1.5-9.4). These results provide support for an association between magnetic field exposure and leukemia. Relative risks for nervous system tumors were close to unity.

Astrocytoma↗
PubMed1996

Occupational exposure to electromagnetic fields and adult leukaemia: a review of the epidemiological evidence.

The relationship between occupational exposure to extremely low-frequency electromagnetic fields and adult leukaemia has been studied extensively during the last decade. The first studies were based on crude exposure assessments, estimated through job titles, with no or only limited control confounding factors. The results were often inconsistent, indicating no effects in about 50% of the studies, while the other half showed only small to moderate effects. Concern has been raised that crude exposure-assessment methods might have diluted the effect estimates, and that improvement of the methods used for exposure assessment would result in more consistent associations. The present review emphasises the latest studies with considerably improved exposure assessments, as well as the control of confounding factors. Results from studies where exposure was assessed through measurements of the magnetic fields at the workplace are still inconsistent. These studies provide some support for the hypothesis of an association between magnetic field exposure and adult leukaemia, especially for chronic lymphocytic leukaemia, but inconsistencies between and within studies weaken the evidence. The lack of consistency regarding the type of leukaemia associated with magnetic field exposure might be explained by differences between the study designs or the populations studied, but based on the existing evidence, no firm conclusions can be drawn.

Adult↗
PubMed1996

Estimating exposure in studies of residential magnetic fields and cancer: importance of short-term variability, time interval between diagnosis and measurement, and distance to power line.

Validity of exposure assessment methods has been a major concern in epidemiologic studies of magnetic field exposure and cancer. We conducted a study to evaluate the relative importance of distance to power lines and calculated historical magnetic fields when estimating past magnetic field exposure. Another goal was to compare results based on various estimates of magnetic field exposure, to assess the importance of short-term variability in magnetic fields, time between diagnosis and measurement, and sources of magnetic field exposure. We used data from a Swedish case-control study of residential exposure to magnetic fields and cancer. Childhood leukemia risk was associated with calculated historical annual average magnetic fields regardless of distance, and the association with distance disappeared when both variables were entered into the same logistic regression model. Relative risks for measurements at the time of the study (contemporary annual average fields, spot calculations, and spot measurements) were all close to or below unity. The results support the hypothesis that the difference between results using historical calculations and spot measurements is explained by the time interval between diagnosis and contemporary magnetic field estimates.

Adolescent↗
PubMed1995

Magnetic fields and childhood cancer--a pooled analysis of two Scandinavian studies.

To test the hypothesis that exposure to magnetic fields, of the type generated by high voltage installations, increases cancer incidence in children, the original data from two case-control studies were pooled. The Swedish study was based on children living within 300 m from transmission lines, and the Danish study on the total population of Denmark. In both these studies, national cancer registries were used to identify cases of leukaemia, lymphoma or central nervous system tumour. Controls were selected randomly from the study populations. Magnetic field exposure was assessed through theoretical calculations of the magnetic fields before the time of diagnosis. An elevated relative risk of childhood leukaemia was found for calculated magnetic field levels of > or = 0.2 microT, estimated at 2.0 (95% CI 1.0-4.1), and for magnetic field levels of > or = 0.5 microT, estimated at 5.1 (95% CI 2.1-12.6). The results support the hypothesis of an association between magnetic fields and childhood leukaemia.

Adolescent↗