Residential characteristics and radiofrequency electromagnetic field exposures from bedroom measurements in Germany.

The objectives of this study were to assess total exposure to radiofrequency electromagnetic fields (RF-EMF) in bedrooms and the contribution of different radioservices (FM radio, analogue TV and DVB-T, TETRA, GSM900 downlink, GSM1800 downlink, UMTS downlink, DECT, and wireless LAN and blue tooth) to the total exposure. Additional aims were to describe the proportion of measuring values above the detection limit of the dosimeters and to characterize the differences in exposure patterns associated with self-reported residential characteristics. Exposure to RF sources in bedrooms was measured using Antennessa(®) EME Spy 120 dosimeters in 1,348 households in Germany; 280 measures were available for each frequency band per household. Mean electrical field strengths and power flux densities were calculated. Power flux densities allow the calculation of proportions of different radioservices on total exposure. Exposure was often below the detection limit (electrical field strength: 0.05 V/m) of the dosimeter. Total exposure varied, depending on residential characteristics (urban vs. rural areas and floor of a building the measurement took place). Major sources of exposure were cordless phones (DECT standard) and wireless LAN/blue tooth contributing about 82% of total exposure (20.5 µW/m(2)). Exposure to RF-EMF is ubiquitous, but exposure levels are-if at all measurable-very low and far below the ICNIRP's exposure reference levels.

Primary brain tumours and specific serum immunoglobulin E: a case-control study nested in the European Prospective Investigation into Cancer and Nutrition cohort.

BACKGROUND: Case-control studies suggest that patients with allergic diseases have a lower risk of developing glioma but not meningioma or schwannoma. However, those data can be differentially biased. Prospective studies with objective measurements of immunologic biomarkers, like immunoglobulin E (IgE), in blood obtained before cancer diagnosis could help to clarify whether an aetiological association exists. METHODS: The present case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) measured specific serum IgE as a biomarker for the most common inhalant allergens in 275 glioma, 175 meningioma and 49 schwannoma cases and 963 matched controls using the ImmunoCAP specific IgE test. Subjects with an IgE level ≥0.35 kUA/l (kilo antibody units per litre) were classified as sensitized by allergens. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by adjusted conditional logistic regression models for each tumour subtype. The effect of dose-response relationship was assessed in five increasing IgE level categories to estimate P-values for trend. RESULTS: The risk of glioma was inversely related to allergic sensitization (OR = 0.73; 95% CI 0.51-1.06), especially pronounced in women (OR = 0.53; 95% CI 0.30-0.95). In dose-response analyses, for high-grade glioma, the lowest OR was observed in sera with the highest IgE levels (P for trend = 0.04). No association was seen for meningioma and schwannoma. CONCLUSION: The results, based on serum samples prospectively collected in a cohort study, provide some support for the hypothesis that individuals with allergic sensitization are at reduced risk of glioma and confirm results from previous case-control studies.

Occupation and risk of glioma, meningioma and acoustic neuroma: results from a German case-control study (interphone study group, Germany).

BACKGROUND: Several epidemiological studies have investigated the association between occupation and brain tumour risk, but results have been inconclusive. We investigated the association between six occupational categories defined a priori: chemical, metal, agricultural, construction, electrical/electronic and transport, and the risk of glioma, meningioma and acoustic neuroma. METHODS: In a population-based case-control study involving a total of 844 cases and 1688 controls conducted from 2000 to 2003, detailed information on life-long job histories was collected during personal interviews and used to create job calendars for each participant. Job title, job activity, job number, and the starting and ending dates of the activity were recorded for all activities with duration of at least 1 year. Reported occupational activities were coded according to the International Standard Classification of Occupations 1988 (ISCO 88). For the analyses we focused on six a priori defined occupational sectors, namely chemical, metal, agricultural, construction, electrical/electronic and transport. Multiple conditional logistic regression analysis was used to estimate odds ratios and their 95% confidence intervals. RESULTS: Most of the observed odds ratios were close to 1.0 for ever having worked in the six occupational sectors and risk of glioma, meningioma and acoustic neuroma. Sub-group analyses according to duration of employment resulted in two elevated odds ratios with confidence intervals excluding unity. CONCLUSIONS: We did not observe an increased risk of glioma or meningioma for occupations in the agricultural, construction, transport, chemical, electrical/electronic and metal sectors. The number of 'significant' odds ratios is consistent with an overall 'null-effect'.

Mobile phone base stations and adverse health effects: phase 2 of a cross-sectional study with measured radio frequency electromagnetic fields.

OBJECTIVE: The aim of the cross-sectional study was to test the hypothesis that exposure to continuous low-level radio frequency electromagnetic fields (RF-EMFs) emitted from mobile phone base stations was related to various health disturbances. METHODS: For the investigation people living mainly in urban regions were selected from a nationwide study in 2006. In total, 3526 persons responded to a questionnaire (response rate 85%). For the exposure assessment a dosimeter measuring different RF-EMF frequencies was used. Participants answered a postal questionnaire on how mobile phone base stations affected their health and they gave information on sleep disturbances, headaches, health complaints and mental and physical health using standardised health questionnaires. Information on stress was also collected. Multiple linear regression models were used with health outcomes as dependent variables (n = 1326). RESULTS: For the five health scores used, no differences in their medians were observed for exposed versus non-exposed participants. People who attributed adverse health effects to mobile phone base stations reported significantly more sleep disturbances and health complaints, but they did not report more headaches or less mental and physical health. Individuals concerned about mobile phone base stations did not have different well-being scores compared with those who were not concerned. CONCLUSIONS: In this large population-based study, measured RF-EMFs emitted from mobile phone base stations were not associated with adverse health effects.

Mobile phone base stations and adverse health effects: phase 1 of a population-based, cross-sectional study in Germany.

OBJECTIVE: The aim of this first phase of a cross-sectional study from Germany was to investigate whether proximity of residence to mobile phone base stations as well as risk perception is associated with health complaints. METHODS: The researchers conducted a population-based, multi-phase, cross-sectional study within the context of a large panel survey regularly carried out by a private research institute in Germany. In the initial phase, reported on in this paper, 30,047 persons from a total of 51,444 who took part in the nationwide survey also answered questions on how mobile phone base stations affected their health. A list of 38 health complaints was used. A multiple linear regression model was used to identify predictors of health complaints including proximity of residence to mobile phone base stations and risk perception. RESULTS: Of the 30,047 participants (response rate 58.6%), 18.7% of participants were concerned about adverse health effects of mobile phone base stations, while an additional 10.3% attributed their personal adverse health effects to the exposure from them. Participants who were concerned about or attributed adverse health effects to mobile phone base stations and those living in the vicinity of a mobile phone base station (500 m) reported slightly more health complaints than others. CONCLUSIONS: A substantial proportion of the German population is concerned about adverse health effects caused by exposure from mobile phone base stations. The observed slightly higher prevalence of health complaints near base stations can not however be fully explained by attributions or concerns.

Environmental risk factors for sporadic acoustic neuroma (Interphone Study Group, Germany).

The only known risk factor for sporadic acoustic neuroma is high-dose ionising radiation. Environmental exposures, such as radiofrequency electromagnetic fields and noise are under discussion, as well as an association with allergic diseases. We performed a population-based case-control study in Germany investigating these risk factors in 97 cases with acoustic neuroma, aged 30 to 69 years, and in 194 matched controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated in multiple logistic regression models. Increased risks were found for exposure to persistent noise (OR=2.31; 95% CI 1.15-4.66), and for hay fever (OR=2.20; 95% CI 1.09-4.45), but not for ionising radiation (OR=0.91; 95 % CI 0.51-1.61) or regular mobile phone use (OR=0.67; 95% CI 0.38-1.19). The study confirms results of recently published studies, although the pathogenetic mechanisms are still unknown.

Lack of association of herpesviruses with brain tumors.

Gliomas are the most frequent primary brain tumors in humans. Many studies have been carried out on their etiology; however, the only confirmed risk factors are hereditary predisposing conditions and high dose of ionizing radiation. Recently, human cytomegalovirus (HCMV) gene products and nucleic acids were reported to be present in all of 27 glioma samples investigated in contrast to other brain tissues, and it was hypothesized that HCMV might play a role in glioma pathogenesis. To evaluate these findings, samples of 40 gliomas, 31 meningiomas, and 6 acoustic neurinomas (ACNs) were analyzed for the presence of HCMV macromolecules using polymerase chain reaction (PCR) and immunohistochemistry. Additionally, corresponding blood samples from 72 patients were analyzed for the presence of HCMV DNA to check for a possible contamination of tumor tissues with HCMV-infected blood cells. No HCMV DNA sequences were found, neither in brain tumor tissues nor in corresponding blood samples. Immunohistochemistry did not detect HCMV-specific proteins. Addressing a possible role of other herpesviruses as has been suggested in seroepidemiological studies, seroprevalence of antibodies to HCMV, herpes simplex virus (HSV), Epstein-Barr virus (EBV), and varicella-zoster virus (VZV) were determined by enzyme-linked immunosorbent assay (ELISA). Serological analyses of brain tumor patients showed no significant differences in the prevalences of antibodies to HCMV, HSV, EBV, or VZV compared to the general population. Thus, the data of the present study do not support the hypothesis of an association of herpesviruses with the development of primary brain tumors.

Contacts with animals and humans as risk factors for adult brain tumours. An international case-control study.

While numerous studies have addressed the possible role of farming and related exposures as risk factors for brain tumours in adults, few of them have examined the potential effect of exposure to farm animals or pets. In an international multicentre case-control study, we investigated whether residence on a farm, contact with animals, or working in occupations with a high degree of potential contact with animals or humans were associated with brain tumours. Using a common questionnaire, 1177 cases of glioma, 330 with meningioma and 2478 controls from eight centres were interviewed about the exposures and, in particular, about their contacts with nine species of animals: dairy cattle, beef cattle, pigs, horses, sheep, goats, poultry, dogs and cats. Living or working on a farm was not a risk factor, for either glioma or meningioma. Except in some centres, there was no relationship between having contacts with farm animals or pets and the risk of brain tumour, for either type of tumour or either sex. In relation to seven industrial groups involving frequent human and/or animal contacts, no association was apparent for either glioma or meningioma. In relation to 25 occupational groups with potential frequent contact with humans and/or animals, for glioma there was a reduced risk for biological technicians (Odds Ratio (OR)/=0, P=0.01), and general farm workers (OR=0.66, 95% Confidence Interval (CI): 0.5-0.9). For meningioma, there was an increased risk for cooks (OR=2.0; CI: 1.2-3.4). With some exceptions, these results indicate no association between either the type of brain tumour and contacts with animals, or with occupations that include a high level of contact with animals or a high level of contact with humans.

Role of medical history in brain tumour development. Results from the international adult brain tumour study.

In an international population-based case-control study carried out in 8 centres in 6 countries, we investigated the role of specific medical conditions in the aetiology of brain tumours in adults. Recruited were 1,178 glioma and 331 meningioma cases and 2,493 age- and gender-matched population controls. Only medical conditions occurring at least 2 years before brain tumour diagnosis were considered. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated using a conditional logistic regression model. Heterogeneity between centres was tested. No association between meningioma and previous medical conditions was observed. For glioma, there was an increased risk associated with epilepsy (RR = 6.55, 95% CI 3.40-12.63), but this was considerably weaker for epilepsy of more than 20 years duration. The risk remained elevated after adjustment for use of anti-epileptic drugs. There was a statistically significant inverse association between glioma and all allergic diseases combined (RR = 0.59, 95% CI 0.49-0.71); this was also observed for specific allergic conditions, namely, asthma and eczema. Subjects who reported a history of infectious diseases (e.g., colds, flu) showed a 30% reduction in risk (RR = 0.72, 95% CI 0.61-0.85). The decreased risks for glioma in subjects reporting a history of allergic conditions or infectious diseases may indicate an influence of immunological factors on the development of glioma. The association between glioma and epilepsy has to be interpreted cautiously and needs further investigation.

[Is there an increased risk of leukemia, brain tumors or breast cancer after exposure to high-frequency radiation? Review of methods and results of epidemiologic studies]. / Gibt es ein erhöhtes Risiko für Leukämien, Hirntumoren oder Brustkrebs nach Exposition gegenüber Hochfrequenzstrahlung?

BACKGROUND: There are only a few epidemiologic studies investigating risk factors in persons occupationally exposed to high-frequency radiation (e.g. radio-, TV-waves, mobile phones or microwaves). The results of the studies are mostly inconsistent. METHODS: All epidemiologic studies which investigated the association between occupational exposure to high-frequency radiation and the risk of leukemia, brain tumors or breast cancer were included in this review. All studies published between 1980 and 1997, such as record-linkage, case-control, and cohort studies, were retrieved from MEDLINE. Incidence and mortality studies are included. Methodologic problems of these investigations are discussed. RESULTS: Most of the recent epidemiologic studies do not present quantitative exposure data or data on the specific frequencies of electro magnetic fields. In general, the relative risks for leukemia, brain tumors or breast cancer are small, not significant and inconsistent. Confounder variables were not included in most of the analyses and no dose-response relationship was reported. CONCLUSION: To increase the power and the validity of the studies a re-analysis based on original data of all previous studies in this field is recommended. Additionally, to investigate the influence of high-frequency radiation on the development of cancer, international epidemiologic studies are necessary. Only they would have sufficient sample size to detect small elevated risks.

Traditional reviews, meta-analyses and pooled analyses in epidemiology.

BACKGROUND: The use of review articles and meta-analysis has become an important part of epidemiological research, mainly for reconciling previously conducted studies that have inconsistent results. Numerous methodologic issues particularly with respect to biases and the use of meta-analysis are still controversial. METHODS: Four methods summarizing data from epidemiological studies are described. The rationale for meta-analysis and the statistical methods used are outlined. The strengths and limitations of these methods are compared particularly with respect to their ability to investigate heterogeneity between studies and to provide quantitative risk estimation. RESULTS: Meta-analyses from published data are in general insufficient to calculate a pooled estimate since published estimates are based on heterogeneous populations, different study designs and mainly different statistical models. More reliable results can be expected if individual data are available for a pooled analysis, although some heterogeneity still remains. Large prospective planned meta-analysis of multicentre studies would be preferable to investigate small risk factors, however this type of meta-analysis is expensive and time-consuming. CONCLUSION: For a full assessment of risk factors with a high prevalence in the general population, pooling of data will become increasingly important. Future research needs to focus on the deficiencies of review methods, in particular, the errors and biases that can be produced when studies are combined that have used different designs, methods and analytic models.

An international case-control study of adult glioma and meningioma: the role of head trauma.

BACKGROUND: Increased brain tumour risk after head trauma suggested by case reports and clinical series has been previously studied epidemiologically with mixed results. An international multicentre case-control study investigated the role of head trauma from injury or sports participation in adult brain tumour risk. METHODS: In all, 1178 glioma and 330 meningioma cases were individually or frequency matched to 2236 controls. Only exposures that occurred at least 5 years before diagnosis and head injuries that received medical attention were considered. RESULTS: Risk for ever having experienced a head injury was highest for male meningiomas (odds ratio [OR] = 1.5, 95% confidence interval [CI] : 0.9-2.6) but was lower for 'serious' injuries, i.e. those causing loss of consciousness, loss of memory or hospitalization (OR = 1.2, 95% CI: 0.6-2.3). Among male meningiomas, latency of 15 to 24 years significantly increased risk (OR = 5.4, 95% CI: 1.7-16.6), and risk was elevated among those who participated in sports most correlated with head injury (OR = 1.9, 95% CI: 0.7-5.3). Odds ratios were lower for male gliomas (OR = 1.2, 95% CI : 0.9-1.5 for any injury; OR = 1.1, 95% CI: 0.7-1.6 for serious injuries) and in females in general. CONCLUSIONS: Evidence for elevated brain tumour risk after head trauma was strongest for meningiomas in men. Findings related to sports should be interpreted cautiously due to cultural variability in our data and our lack of complete data on physical exercise in general which appeared to be protective.

Diet, obesity and risk for renal cell carcinoma: results from a case control-study in Germany.

Increasing incidence of renal cell carcinoma in Western countries raises particular attention to its etiology. Diet may be related to risk for renal cell carcinoma since obesity has been linked with this malignant condition. A case-control study with 277 incident renal cell cancer patients (ICD 189.0) and 286 population controls was conducted in the Rhein-Neckar-Odenwald area, Germany, in the period of 1989 to 1991. The core study protocol included a face-to-face interview about demographical parameters, previous diseases, medication, tobacco smoking, occupational history, occupational exposures, beverage consumption, and obesity. In addition, study participants were asked to fill in a self-administered food frequency questionnaire with 122 food items to estimate overall food intake. Fifty-six % of the cases and 74% of the controls participated in this part of the study (n = 155 cases and 212 controls). This was 47% of the original cases (n = 328) and 56% of the controls (n = 381). No selection bias could be identified with regard to age group, gender, educational status or recent BMI in the analyzed group compared with the eligible cases and controls. Relative risk (RR) estimates for tertiles of consumption revealed a significantly increased risk with increasing intake of fat spread (RR of high intake compared to low intake: 1.90 (95% CI 1.08-3.32)). Increased risk was also found for intake of meat and meat products (RR of high intake compared to low intake: 1.71 (95% CI 0.96-3.04)) and energy adjusted fat (RR of high intake compared to low intake: 1.64 (95% CI 0.95-2.83)). A decreased risk was seen with increasing intake of fruit (RR of high intake compared to low intake: 0.40 (95% CI 0.23-0.69)) and of vitamin C (RR of high intake compared to low intake: 0.62 (95% CI 0.37-1.05)). Beverage consumption, preparation of food and eating pattern were not linked with risk of renal cell cancer. The relative risk estimates of spreading fat (sauce and vitamin C intake were tested in two models, with and without including BMI as covariate. In both models significant associations of these nutritional variables with risk for renal cell cancer remained. The current results indicate that specific food pattern associated with obesity explain differences in incidence of renal cell carcinoma in industrialized countries.

[Limitations of meta-analysis from published data in epidemiological research]. / Grenzen von Metaanalysen aus publizierten Daten bei epidemiologischen Fragestellungen.

Metaanalyses of epidemiological studies have increased during the last years and are often used to evaluate the effect of risk factors which are inconsistent in different studies, mainly for small risk factors. Very often a metaanalysis is performed from published data. In this article we discuss this form of a metaanalysis and investigate whether the requirement to get reliable information is achievable with it. We mainly ask questions whether qualitative and quantitative dose-response analysis can be performed. We point out the differences between metaanalysis from experimental data and clinical randomized studies and epidemiological studies. We discuss different arguments that were given for performing metaanalysis in clinical trials and investigate whether they are also valid in observational studies. We mainly concentrate on the problem of estimating a single pooled risk estimate. Two examples from literature are used to show problems with metaanalysis from published data.

International renal-cell-cancer study. VI. the role of medical and family history.

A number of medical conditions have been linked with renal-cell cancer, although the evidence is not consistent in every case. In a large international case-control study of renal-cell cancer, we examined, among other hypotheses, associations with a personal history of certain medical conditions and a family history of cancer of the kidney or thyroid. Relative risks (RR), adjusted for the effects of age, gender, body-mass index, tobacco smoking and study centre, were significantly increased by a history of kidney stones or thyroid or kidney disease. The RR were not altered by additional adjustment for hypertension, or when diagnoses were restricted to those made at least 5 or 10 years before 1987 (the usual "cut-off" date). The link with kidney injury is particularly likely to be affected by recall bias. Increased RR of borderline significance were found for kidney infection (RR, 1.2) and diabetes (RR, 1.4). Having one first-degree relative with kidney cancer was associated with a significantly increased risk of renal-cell cancer (RR, 1.6; 95% Cl, 1.1-2.4). Seven cases reported 2 first-degree relatives with kidney cancer. No controls had first-degree relatives with kidney cancer. None of our participants reported having von Hippel-Lindau disease. The data suggests that a few conditions of the kidney are strongly associated with renal-cell cancer and that heredity plays a role in a small proportion of cases.

Sero-epidemiological analysis of the risk of virus infections for childhood leukaemia.

Virus infections have been thought to be involved in the development of childhood leukaemia. In order to address this issue we determined, in a case-control study, the prevalence of antibodies to viruses infecting blood or bone-marrow cells [Epstein-Barr virsus (EBV), human herpes virus type 6 (HHV-6), parvovirus B19] as well as to the human virus known for its tumour-suppressive properties, the adeno-associated virus type 2 (AAV-2), in the sera of 121 children with leukaemia in Germany, and in 197 control individuals, hospitalized for other reasons, and matched for age and gender to the cases. In addition, we developed a questionnaire to be answered by the children's parents, in order to gain information on previous infections of the children as well as to calculate for factors which may influence serological findings. Comparative determination of the prevalence of antibodies against AAV-2, B-19 or HHV-6 revealed no significant differences in cases and controls. However, antibodies to EBV were more frequently found in children with leukaemia younger than 6 years of age (age at the time of diagnosis of leukaemia) than in controls. Apparently, infection with AAV-2 has no protective effect in childhood leukaemia, in contrast to results observed for other malignancies. Similarly, and in accordance with results on leukaemia in adults, we found no indication of a protective effect of infection with the parvovirus B-19. The data suggest that EBV, which is known to be involved in various lymphomas, may play a role in the development of childhood leukaemia in young children.

International renal-cell cancer study. VIII. Role of diuretics, other anti-hypertensive medications and hypertension.

Risk of renal-cell cancer in relation to use of diuretics, other anti-hypertensive medications and hypertension was assessed in a multi-center, population-based, case-control study conducted in Australia, Denmark, Germany, Sweden and the United States, using a shared protocol and questionnaire. A total of 1,732 histologically confirmed cases and 2,309 controls, frequency-matched to cases by age and sex, were interviewed. The association between renal-cell cancer and the drugs was estimated by relative risks (RRs) and 95% confidence intervals (CIs). Risks were increased among users of diuretics and other anti-hypertensive medications. After adjustment for hypertension, risk for diuretics was reduced to unity, except among long-term (15+ years) users. Risk for use of non-diuretic anti-hypertensive drugs remained significantly elevated and increased further with duration of use. Overall risk was not enhanced when both classes of medications were used. Excess risk was not restricted to any specific type of diuretic or anti-hypertensive drug and no trend was observed with estimated lifetime consumption of any particular type of product. The RR for hypertension after adjustment for diuretics and other anti-hypertensive medications was 1.4 (95% CI = 1.2-1.7), although among non-users of any anti-hypertensive medications, there was little excess risk associated with a history of hypertension. Exclusion of drug use that first occurred within 5 years of cancer diagnosis or interview did not alter the associations. Our findings suggest small effects on renal-cell cancer risk associated with hypertension and use of diuretics and other anti-hypertensive medications. However, because of potential misclassifications of these highly correlated variables, it is difficult to distinguish the effect of treatment from its indication, hypertension.

International renal-cell cancer study. IV. Occupation.

The relationship between renal-cell cancer (RCC) and occupation was investigated in an international multicenter population-based case-control study. Study centers in Australia, Denmark, Germany, Sweden and the United States interviewed 1732 incident RCC cases and 2309 controls. Significant associations were found with employment in the blast-furnace or the coke-oven industry [relative risk (RR), 1.7; 95% confidence interval (CI), 1.1-2.7], the iron and steel industry (RR, 1.6; 95% CI, 1.2-2.2) and exposure to asbestos (RR, 1.4; 95% CI, 1.1-1.8), cadmium (RR, 2.0; 95% CI, 1.0-3.9), dry-cleaning solvents (RR, 1.4; 95% CI, 1.1-1.7), gasoline (RR, 1.6; 95% CI, 1.2-2.0) and other petroleum products (RR, 1.6; 95% CI, 1.3-2.1). Asbestos, petroleum products and dry-cleaning solvents appear to merit further investigation, in view of the relationship between risk and duration of employment or exposure and after adjustment for confounding. There was a negative association between RCC and education, but it was not consistent across all centers. Overall, the results of our multicenter case-control study suggest that occupation may be more important in the etiology of RCC than indicated by earlier studies.

International renal-cell cancer study. V. Reproductive factors, gynecologic operations and exogenous hormones.

The relationships between reproductive factors, exogenous hormones and renal-cell cancer were examined in an international, multicenter, population-based, case-control study undertaken in 1989-1991. Data from 5 centers situated in Australia, Denmark, Germany, Sweden and the United States included for analysis 608 women with renal-cell cancer and 766 female controls. A significant trend in risk (p = 0.002) was associated with number of births, with an 80% excess risk for 6 or more births [RR = 1.8, 95% confidence interval (CI) = 1.1 to 2.9] compared with one birth. A decreasing risk was seen for increasing age at first birth, although this was confounded by body-mass index and number of births. A suggestive reduction of risk was also seen for increasing age at menarche. Age at menopause was unrelated to risk of renal-cell cancer. An increased risk was observed for women having had both a hysterectomy and an oophorectomy. Use of oral contraceptives in non-smoking women reduced the risk of renal-cell cancer (RR = 0.5, 95% CI = 0.4 to 0.8); this reduction increased with longer duration of use. No association was observed for estrogen replacement therapy. Our results indicate that certain hormonal and reproductive variables may be related to risk of renal-cell cancer and deserve further investigation, both epidemiologically and experimentally.