Decreased leptin levels in normal weight women with hypothalamic amenorrhea: the effects of body composition and nutritional intake.

Leptin is a protein encoded by the ob gene and expressed in adipocytes. A sensitive marker of nutritional status, leptin is known to correlate with fat mass and to respond to changes in caloric intake. Leptin may also be an important mediator of reproductive function, as suggested by the effects of leptin infusions to restore ovulatory function in an animal model of starvation. We hypothesized that leptin levels are decreased in women with hypothalamic amenorrhea and that leptin may be a sensitive marker of overall nutritional status in this population. We, therefore, measured leptin levels and caloric intake in 21 women with hypothalamic amenorrhea (HA) and 30 age-, weight-, and body fat-matched eumenorrheic controls. Age (24 +/- 5 vs. 24 +/- 3 yr), body mass index (20.6 +/- 1.3 vs. 21.1 +/- 1.5 kg/m2), percent ideal body weight (94.9 +/- 5% vs. 96.3 +/- 6.3%), and fat mass (14.2 +/- 3.6 vs. 15.5 +/- 2.9 kg, determined by dual energy x-ray absortiometry) did not differ between the groups. Leptin levels were significantly lower in the HA subjects compared with those in the controls (7.1 +/- 3.0 vs. 10.6 +/- 4.9 micrograms/L; P = 0.005). Total caloric intake (1768 +/- 335 vs. 2215 +/- 571 cal/day; P = 0.003), fat intake (333 +/- 144 vs. 639 +/- 261 cal/day; P < 0.0001), and insulin levels (5.6 +/- 1.2 vs. 7.4 +/- 3.2 microU/mL; P = 0.015) were lower in the women with HA than in the eumenorrheic controls. The difference in leptin levels remained significant after controlling for insulin (P = 0.023). These data are the first to demonstrate hypoleptinemia, independent of fat mass, in women with HA. The hypoleptinemia may reflect inadequate calorie intake, fat intake, and/or other subclinical nutritional disturbances in women with HA. The mechanism and reproductive consequences of low leptin in this large population of women remain unknown.

Breast cancer and electromagnetic fields--a review.

PURPOSE: Several statements have been issued to the effect that no consistent, significant link has been demonstrated between cancer and electromagnetic fields (EMF). However, there continues to be much interest in a possible association with breast cancer, in part because breast cancer risk is substantially higher in industrialized countries than in other areas, and electric power generation and consumption is one of the hallmarks of industrialized societies. In 1987, Stevens proposed a biological mechanism whereby two products of electric power generation, EMF and light at night, might contribute to mammary carcinogenesis through inhibition of melatonin. METHODS: We conducted a comprehensive review of the epidemiologic literature and hypothesized mechanisms pertaining to EMF exposure and the risk of breast cancer, in order to assess whether or not there was evidence to suggest a link between EMF and breast cancer. RESULTS: Some occupational epidemiological studies have demonstrated an increased incidence of breast cancer among mainly male electrical workers. It has been difficult to study women, as few are employed in these types of occupations. In all, there have been eleven occupational studies related to breast cancer in women, and statistically significant risk ratios have been observed: 1.98 for pre-menopausal women in occupations with high EMF exposure in one study, 2.17 in all women who worked as telephone installers, repairers, and line workers in another study, and 1.65 for system analysts/ programmers, 1.40 for telegraph and radio operators, and 1.27 for telephone operators in a third study. However, six of the studies did not find any significant effects and two found effects only in subgroups. The results of the eight studies of residential exposure and four electric blanket studies have been inconsistent, with most not demonstrating any significant association. However, this might be attributed, at least to some extent, to difficulties in assessing residential exposure in these studies, as well as other methodological considerations. CONCLUSIONS: The biologic plausibility of an association between EMF and breast cancer, coupled with suggestive data from occupational studies and unexplained high incidence rates of breast cancer, suggests that further investigation of this possible association is warranted.

Recruiting participants for community-based research: the Diabetic Retinopathy Awareness Program.

PURPOSE: Recruiting participants is a major challenge for population studies. We present the recruitment methods followed by the Diabetic Retinopathy Awareness Program (DRAP), a community-based, randomized, masked, controlled trial to meet and exceed its sample size goals. METHODS: A county-wide multi-media promotional campaign to recruit and enroll participants in the trial was planned and executed from October 1993 through April 1994, with the assistance of the local news media and community and professional groups. A toll-free 800 number recruitment line was established, and postage-paid recruitment postcards distributed. The trial was designed to examine whether a mailed educational intervention could increase compliance with vision care guidelines among persons with diabetes in the community. RESULTS: A total of 2308 persons with diabetes were interviewed for eligibility and 813 enrolled in the intervention trial, exceeding the original recruitment goals of 1800 and 600, respectively. Those who completed the enrollment interview reflected county demographics. During recruitment, newspaper, television and radio stories featured the study; pharmacies and physician offices displayed study materials; public service announcements appeared in local print and broadcast media. The largest single recruitment response was a local television news report, followed by a newspaper story. CONCLUSIONS: These experiences substantiate the need for a comprehensive coordinated approach, using planned multiple sources, to achieve recruitment success. By engaging the lay and professional communities along with the media, recruitment costs can be kept to a minimum. Participant costs can be minimized by employing a toll-free number and eliminating study participant travel, thus allowing for inclusion of traditionally underserved populations. This approach is applicable to other studies, where community-based participation is desired.

Design features of the Diabetes and Periodontal Therapy Trial (DPTT): a multicenter randomized single-masked clinical trial testing the effect of nonsurgical periodontal therapy on glycosylated hemoglobin (HbA1c) levels in subjects with type 2 diabetes and chronic periodontitis.

BACKGROUND: Evidence suggests that periodontitis is associated with prevalent and incident type 2 diabetes mellitus (T2DM), raising the question of whether periodontitis treatment may improve glycemic control in patients with T2DM. Meta-analyses of mostly small clinical trials suggest that periodontitis treatment results in a modest reduction in glycosylated hemoglobin (Hb) A1c. PURPOSE: The purpose of the Diabetes and Periodontal Therapy Trial (DPTT) was to determine if periodontal treatment reduces HbA1c in patients with T2DM and periodontitis. METHODS: DPTT was a phase-III, single-masked, multi-center, randomized trial with a planned enrollment of 600 participants. Participants were randomly assigned to receive periodontal treatment immediately (Treatment Group) or after 6 months (Control Group). HbA1c values and clinical periodontal measures were determined at baseline and 3 and 6 months following randomization. Medication usage and dosing were assessed at each visit. Periodontal treatment consisted of scaling and root planing for a minimum of two 90-minute sessions, plus the use of an antibacterial mouth rinse for at least 32 days afterwards. The primary outcome was change in HbA1c from baseline to 6 months and the trial was powered to detect a between-group difference of 0.6%. Secondary outcomes included changes in periodontal clinical measures, fasting plasma glucose, the Homeostasis Model Assessment (HOMA2) and the need for rescue diabetes or periodontal therapy. CONCLUSION: Dental and medical researchers collaborated to recruit, treat and monitor participants with two chronic diseases to determine if treatment of one condition affects the status of the other.

Divine intervention and the treatment of chemical dependency.

Alcoholics Anonymous and related 12-step programs are the predominant influence on chemical dependency treatment programs in the United States today. 12-step programs have a strong religious orientation, despite rationalizations that Higher Power need not mean the traditional definition of God. The teaching of religious beliefs is not a proper function of therapists treating addictions in a general population. Moreover, teaching patients they can only recover through the intervention of a Higher Power locks them into a pattern of dependence on something outside themselves in order to function. 12-step programs have helped millions of people. Even more could be helped were they to eliminate the concept of needing a Higher Power.

Diabetes mellitus and cancer risk: a multisite case-control study.

The association between a prior diagnosis of diabetes mellitus and cancer was examined in a large multisite case-control study based on interviews of 8220 white males and 6690 white females aged 30-89 who were admitted to Roswell Park Memorial Institute between 1957 and 1965 for the diagnosis and treatment of cancer. A prior history of diabetes mellitus as diagnosed by a physician was examined as a risk factor for cancer by conducting sex- and site-specific comparisons with a common control group of 2363 white males and 2475 white females who were admitted to the same hospital during the same years, but were found not to have cancer. The findings are consistent with previous studies which have shown diabetes to be a risk factor for cancer of the uterine corpus. A positive association was also noted between diabetes and cancer of the vulva and vagina. The evidence for excess estrogen levels as the underlying mechanism for increased risk of uterine and vulvo-vaginal cancer is reviewed. No consistent association between diabetes and pancreatic cancer was observed in this study, except when those cases in which diabetes was diagnosed within a year before the diagnosis of pancreatic cancer were included. This suggests that diabetes may be an early presenting sign of pancreatic cancer rather than a risk factor. A positive association between prior diagnosis of diabetes was noted for kidney cancer and nonmelanoma skin cancer in females only. No association between type of treatment (i.e. insulin, oral agents) and cancer risk was noted.

The distribution of immunocompetent cells in the compartments of the palatine tonsils in bacterial and viral infections of the upper respiratory tract.

Employing a series of monoclonal antibodies directed against T cell subsets using the avidin-biotin complex method as the immunoperoxidase technique and using fluorescein-conjugated antisera directed against the major immunoglobulins, we have studied the distribution of immunocompetent cells in sections of tonsils from 21 patients with various inflammatory diseases of the tonsils, including Streptococcal tonsillitis, recurrent tonsillitis and tonsillitis associated with infectious mononucleosis. The following conclusions can be made in regard to our study. The percentage of T cells decreases in all compartments of the tonsils with increasing episodes of tonsillitis as well as with infectious mononucleosis and Streptococcal tonsillitis. Similarly, the percentage of HLA-DR positive cells decreases with increasing episodes of tonsillitis and is statistically significant in the mantle zone. The percentage of IgM B cells and IgD B cells tends to increase in the extrafollicular zone and decrease in the mantle zone with increasing episodes of tonsillitis as well as with increasing age. The percentage of IgG and IgA plasma cells is highest in children who have had 3-5 episodes of tonsillitis, but markedly decreases in the follicle and extrafollicular compartments in patients who have had more than 5 episodes of tonsillitis. FACS analysis of B cells in the tonsils and peripheral blood show a marked decrease in IgD in both the tonsil and the peripheral blood and a significant increase of IgG in the peripheral blood. These findings may suggest late clonal expansion of B cells in recurrent tonsillitis and Streptococcal tonsillitis. Finally, the distribution of immunocompetent cells in recurrent tonsillitis, Streptococcal tonsillitis and tonsillitis associated with infectious mononucleosis appears to be independent of age.

Recent epidemiologic studies on nutrition and cataract in India, Italy and the United States.

Three independent case-control studies with similar methodologies were conducted in India, the United States and Italy to investigate risk factors by cataract type. Their common objectives were to evaluate risk factors for each cataract type, giving priority to nutritional factors, and to determine whether risk factors differed among cataract types. Data included self-reporting of food frequencies and various biochemical determinations. A higher body mass index was the only nutritional factor found by more than one study to be associated with cataract, being less frequent in cases than in controls. Blood nutritional status from one study showed that a high antioxidant index decreased risk for at least one cataract type, high glucose-6-phosphate dehydrogenase values increased risk for at least one cataract type, a high albumin globulin ratio decreased risk for mixed cataract, and high iron levels decreased risk for cortical cataract. Only one of the three studies found that a high nutritional status, high dietary antioxidant index, and use of multiple vitamin supplements decreased risk for cataract. Findings from these studies suggest socioeconomic and nutritional components to cataract risk, although not consistently across studies or cataract types. Differences between studies may be due to differences in populations and/or data collection methods. Because reducing cataract risk would have major implications for a large segment of the population, clinical trials seem appropriate to confirm and evaluate the potentially modifiable risk factors suggested by these studies.

Standard information on environmental exposure linked to data on cancer patients, with a brief review of the literature.

A review of national resources presently available for linking cancer morbidity and mortality data with information on environmental factors is presented. Additional sources of data on exposure, obtained directly from the patient or from his/her hospital record, are discussed. At the patient level, an interview questionnaire records standardized data on residential and occupational experiences and on a variety of life-style factors such as smoking, alcohol, nutrition, medication, and exercise. At the hospital level, a simple model "exposure registry" is presented which, at minimal cost, would facilitate the collection of limited data on smoking and employment (occupation/business) from the in-patient hospital admission form and from the medical and nursing notes in the patient's record. Both of these instruments represent efforts toward the development of standardized data sets on environmental and personal exposures which would constitute valuable additions to data already collected by the worldwide network of cancer registries.

Patterns of milk consumption and risk of cancer.

The reported milk consumption habits of 3,334 cancer patients and 1,300 comparable control subjects seen at Roswell Park Memorial Institute were studied. The cancer patient group included persons diagnosed with cancers of the oral cavity, stomach, colon, rectum, lung, breast, uterus, cervix, prostate, or bladder. Data were obtained by means of a standardized admissions questionnaire. As a group, control patients were more likely to report never drinking whole milk; cancer patients more often reported frequent consumption of whole milk. Relative risks of different patterns of milk consumption for specific cancer diagnoses, adjusted for sex, age, smoking history, education, and county of residence, were calculated with multiple logistic regression analysis. Elevated risks for frequent consumption of whole milk relative to not drinking milk were observed for cancers of the oral cavity, stomach, colon, rectum, lung, bladder, breast, and cervix. Reduced risks for frequent consumption of 2% milk relative to not drinking milk were observed for cancers of the oral cavity, stomach, rectum, lung, and cervix. Preference for exclusive consumption of reduced-fat milk was linked to significant risk reduction for oral and cervical cancers, and drinking only whole milk was linked to significant risk increases for cancers of the oral cavity, stomach, rectum, lung, and breast. Some associations were observed for a computed index of milk fat intake, but the overall pattern of effects was not fully explained by variations in fat content. The effects observed for some sites may be confounded by other dietary or nondietary correlates of risk.

The surgical management of "in situ" melanoma.

The concept of melanoma "in situ" is discussed pointing out that these lesions have the potential to become invasive tumors if not adequately treated. If such a pathologic diagnosis is made, each margin of the specimen should be carefully checked for the presence of atypical melanocytes. In our experience, with excision margins of 0.5-1 cm, local recurrence has not been a problem.

The planning, execution, and evaluation of a breast cancer detection awareness program.

A Breast Cancer Detection Awareness Program (BCDAP) was conducted in Western New York during the spring of 1987 in conjunction with a national effort by the American Cancer Society. The importance of screening mammography was promoted by public education through the media combined with promotion of breast cancer screening services available from 26 health care providers. Women were instructed to call a hot line to receive a coupon for a low-cost mammogram, if eligible to participate. A provider directory was included to facilitate scheduling appointments. The program resulted in 6,355 women requesting a coupon. From this population 3,178 women utilized the coupon to receive a mammogram. Although the screening rate of 50% was encouraging, approximately half of the callers to the hot line did not receive a mammogram. To increase the screening rate in future programs, it would be useful to determine why some women did not take advantage of the discount coupon.

Women's knowledge and beliefs about breast cancer risk factors, symptoms, detection methods, and treatments.

This paper presents results from a survey of adult women that assessed knowledge, beliefs, and practices regarding the causes, symptoms, detection methods, and treatment of breast cancer. The study population was determined through random selection of household telephone numbers from the Buffalo, New York area telephone directory. Completed interviews were collected from 563 women over the age of 18. Telephone interviews were conducted by trained interviewers, between April and July of 1985. Survey results are compared to those found in the 1979 National Cancer Institute nationwide survey on breast cancer to evaluate if ther have been changes in public awareness about the disease. Differences in knowledge, beliefs, and practices regarding breast cancer were also studied in relation to age, race, and educational background. Overall, women's knowledge about breast cancer has significantly increased since the 1979 survey. However, while more women can name mammography as a diagnostic tool only 15% of women who have heard of mammography reported having had a mammogram. Generally, younger women, white women and those with some college education were more knowledgeable about breast cancer risk factors, symptoms, detection methods, and treatments. Results from this study suggest that although knowledge about breast cancer has improved, women have not adopted recommended early detection practices. Special efforts need to be directed toward health professionals, making mammography more accessible to women who are nonwhite, older and with no college education.

Interhospital differences in cancer survival.

We examined variations in cancer survival rates among a large number of hospitals in the United States. Survival rates for breast cancer, prostate cancer, and Hodgkin's disease were calculated from patient care studies of the American College of Surgeons and were linked to data on hospital characteristics from the surveys of the American Hospital Association. When patient, disease, treatment, and institutional characteristics were examined in multivariate analyses, medical school affiliation, residency training, and community size were not related to hospitals' cancer survival experience. Patterns of care involving greater use of staging laparotomy with splenectomy for Hodgkin's diseases, lesser use of mastectomy without axillary dissection for breast cancer and, greater use of bone scanning and lesser use of hormone therapy for prostate cancer all were associated with better survival. The differences between hospitals' survival rates were large but we found that the differences were more a function of patient characteristics, disease stage, and tumor histology than of hospital affiliations, location, size, facilities, or treatment patterns. These findings provide some data upon which future public health interventions to affect cancer mortality may be planned and evaluated.

Patterns of adherence to diabetes vision care guidelines: baseline findings from the Diabetic Retinopathy Awareness Program.

OBJECTIVES: (1) To describe baseline patterns of adherence to American Diabetes Association and American Academy of Ophthalmology vision care guidelines for diabetes in the Diabetic Retinopathy Awareness Program, and (2) to evaluate factors associated with nonadherence. This paper describes the baseline characteristics of a population enrolled in a prospective, randomized clinical trial. DESIGN: Cross-sectional study. PARTICIPANTS: Between October 1993 and May 1994, the study identified 2308 persons with diabetes, 18 years of age or older, who were residents of Suffolk County, New York, via a multimedia community-wide recruitment campaign. INTERVENTION AND METHODS: Eligibility for the trial was determined during a 20-minute phone interview, which included questions about vision care practices; diabetes management; and knowledge, attitudes, and beliefs about diabetes, vision, and diabetic retinopathy. This paper describes these patient characteristics at baseline. Eligible patients would be randomized subsequently to a 2-year diabetes educational intervention arm, which included mailed packets and newsletters focused on vision care, or to a control nonintervention arm. MAIN OUTCOME MEASURE: Nonadherence to guidelines at baseline was defined as the absence of a dilated eye examination during the year before recruitment into the study. RESULTS: Of the 2308 persons interviewed, 813 (35%) did not follow the vision care guidelines; two thirds of this group reported no eye examination in the year before the interview, and one third had an undilated examination. Ophthalmologists performed 49% of the examinations in the nonadherent group, versus 86% in the adherent group. In logistic regression analyses, factors related to nonadherence were: younger age (odds ratio [OR] = 0.97), type 2 diabetes with or without insulin use (OR = 1.62 and 1.99, respectively), shorter diabetes duration (OR = 0.97), last eye examination performed by an optometrist (OR = 5.32) or other nonophthalmologist (OR = 4.29), less practical knowledge about diabetes (OR = 1.57), and no prior formal diabetes education (OR = 1.30). CONCLUSIONS: Within this population, more than one third of participants had not been following vision care guidelines. Nonadherence was linked to several potentially modifiable factors; changes in these factors could enhance the early detection of diabetic retinopathy.

Survival of the older patient compared with the younger patient with Hodgkin's disease. Influence of histologic type, staging, and treatment.

Age as an independent risk factor for survival of Hodgkin's disease (HD) was investigated using data for the 6345 patients in the American College of Surgeons, Patterns of Care Study. Patients were divided into those 15 to 34 years of age, and those older than 50 years. Older patients had higher rates of advanced stage and B symptoms (e.g., Stage IVB, 19.7% compared with 7.7%) and significantly higher rates of poor prognosis histologic types, odds ratio (OR) = 3.7. The older population with clinical stage (CS) I and II disease was also less likely to have received any of the selected staging procedures, bone marrow biopsy, lymphogram, or laparotomy (OR = 4.48). The two populations were equivalently understaged when CS was compared with pathologic stage (PS). In each category the older patients were more likely to have received no therapy; for PS I and II disease the OR for older patients compared with the younger patient was 2.14. When stratified by PS, B symptom status, histologic type, and treatment the older patients continued to show poorer 5-year survival by the life-table method. The authors' hypothesis--that older patients equivalently staged and treated would have no significant difference in long-term survival--was not substantiated by the data. However, in the analyses in which corrections for the known risk factors were made, the difference in survival was not as great as that in the crude, unstratified data. This study, as well as other recent studies utilizing smaller numbers of patients, finds age an independent predictor of poorer survival in HD patients.

Antioxidant vitamins and nuclear opacities: the longitudinal study of cataract.

OBJECTIVE: The association of antioxidant nutrients and risk of nuclear opacification was evaluated in the Longitudinal Study of Cataract. DESIGN: Nutritional data were collected at baseline on the 764 participants, which included assessment of dietary intake, use of vitamin supplements, and plasma levels of vitamin E. Ophthalmologic and other data were collected at baseline and at yearly follow-up visits, including lens photographs, which were graded using the Lens Opacities Classification System III protocol. MAIN OUTCOME MEASURES: Analyses examined whether the nutritional factors at baseline were related to increases in nuclear opacification at follow-up. The MULCOX2 approach, an extension of the Cox regression model, was used. Results are presented as relative risks (RRs) and 95% confidence intervals. INTERVENTION: Intervention was not applicable. RESULTS: The risk of nuclear opacification at follow-up was decreased in regular users of multivitamin supplements (RR = 0.69; 0.48-0.99), vitamin E supplements (RR = 0.43; 0.19-0.99), and in persons with higher plasma levels of vitamin E (RR = 0.58; 0.36-0.94). CONCLUSIONS: In regular users of multivitamin supplements, the risk of nuclear opacification was reduced by one third; in regular users of vitamin E supplements and persons with higher plasma levels of vitamin E, the risk was reduced by approximately half. These results are similar to those obtained in our earlier case-control study. Because these data are based on observational studies only, the results are suggestive but inconclusive. The possible effect of nutritional supplements on the lens requires confirmation by ongoing clinical trials.

Incidence and progression of cortical and posterior subcapsular opacities: the Longitudinal Study of Cataract. The LSC Group.

OBJECTIVE: The purpose of the study is to estimate incidence and progression rates of cortical and posterior subcapsular (PSC) opacities in the Longitudinal Study of Cataract (LSC). DESIGN: An epidemiologic study of the natural history of lens opacities in a clinic-based population. PARTICIPANTS: The LSC was based on 764 participants in an earlier case-control study of lens opacities. MAIN OUTCOME MEASURES: Baseline data, collected until 1988, included color slit and retroillumination photographs. The same data were collected at follow-up visits from 1989 to 1993. The Lens Opacities Classification System III (LOCS III) was used to assess lens changes between baseline and follow-up photographs. The product-limit method was used to estimate the incidence and progression rates. RESULTS: After 5 years of follow-up, the incidence rates for developing cortical and PSC opacities were 7.7% and 4.3%, respectively. The progression rate of pre-existing cortical opacities was 16.2% after 5 years, and was twice as high as the incidence rate. The progression of pre-existing PSC opacities was much higher, and reached 55.1% after 5 years of follow-up. The incidence of newly developed cortical or PSC opacities increased with age. The incidence of PSC opacities also increased when coexisting opacities were present at baseline. CONCLUSIONS: After 5 years, 1 in every 13 patients developed new cortical opacities, and 1 in 24 developed new PSC opacities. The 5-year progression rates for cortical and PSC opacities were much higher than the incidence rates. These results can be used to estimate the rate of cortical and PSC changes in similar populations.

Risk factors for nuclear opalescence in a longitudinal study. LSC Group. Longitudinal Study of Cataract.

This study evaluated risk factors for increases in nuclear opacification of the lens in the Longitudinal Study of Cataract (1989-1993; Boston, Massachusetts), which included 764 participants. Baseline data on demographic, medical, and other risk factors were available from an earlier case-control study; follow-up visits were completed yearly over a 4-year period. The lens photographs taken at baseline and at each follow-up visit were graded using the Lens Opacities Classification System III protocol. Analyses evaluated which risk factors collected at baseline were related to increased nuclear opacification at follow-up. The MULCOX2 method, an extension of Cox regression for nested event-time data, was used to estimate the effects of the risk factors. This method accounted for the correlation between fellow eyes. Results showed that the risk of nuclear opacification increased with each year of age (relative risk (RR) = 1.07), white race (RR = 2.94), lower education (RR = 1.50), use of gout medications (RR = 2.32), current smoking (RR = 1.58), family history of cataract (RR = 1.39), and preexisting posterior subcapsular opacities (RR = 6.67). An association with early use of eyeglasses was also suggested (RR = 1.37). In conclusion, nuclear opacification was related to demographic and other variables, including potentially modifiable factors such as current smoking and use of gout medications. Most risk factors identified by this longitudinal study confirm those found by the original case-control study. The increased risk of nuclear opacities in whites appears to be a new finding.

Magnetic field exposure assessment: a comparison of various methods.

The accurate and valid measurement of personal exposure to magnetic fields poses a major challenge for epidemiologic studies. When considering the various methods to assess exposure, it is unclear which measures are most relevant for studies of human disease, if any. Given these uncertainties, the Electromagnetic Fields and Breast Cancer on Long Island Study (EBCLIS) undertook a pilot study to develop the data collection protocol for a case-control study of breast cancer and magnetic fields. The pilot study used and compared various methods to assess residential exposures to magnetic fields, and related these measures to personal exposures. It included 31 women without breast cancer (mean age, 63+/-7 yr) who lived in their present homes for at least 15 yr. The pilot study consisted of an in-home interview, spot and 24-h magnetic field waveforms and broadband recordings, ground currents, wire coding, and personal 24-h broadband measurements. From the regression analyses, the model that best predicted personal magnetic field exposures included 24-h measurements in the bedroom and in the most lived-in room; as well as ground current test loads taken at the center of this most lived in room (r(2)=86%). The addition of other variables in this regression model yielded only small and nonsignificant increases in r(2). As a direct result of this pilot, EBCLIS will include ground current measurements in its protocol, which have not previously been collected as part of an epidemiologic study. Ground currents may be important because they may be richer in 180 Hz components than are the other currents in a power system. EBCLIS will have the opportunity to examine the ground-current hypothesis in the context of female breast cancer.