ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

To study the effect of magnetic fields on the risk of miscarriage, we conducted a population-based prospective cohort study among pregnant women within a large health maintenance organization. All women with a positive pregnancy test at less than 10 weeks of gestation and residing in the San Francisco area were contacted for participation in the study. We conducted in-person interviews to obtain information on risk factors for miscarriage and other potential confounders. All participants were also asked to wear a magnetic field-measuring meter for 24 hours and to keep a diary of their activities. Pregnancy outcomes were obtained for all participants by searching the health maintenance organization’s databases, reviewing medical charts, and telephone follow-up. We used the Cox proportional hazard model for examining the magnetic field-miscarriage association. A total of 969 subjects were included in the final analyses. Although we did not observe an association between miscarriage risk and the average magnetic field level, miscarriage risk increased with an increasing level of maximum magnetic field exposure with a threshold around 16 milligauss (mG). The rate ratio (RR) associated with magnetic field exposure ≥16 mG (vs<16 mG) was 1.8 [95% confidence interval (CI) = 1.2–2.7]. The risk remained elevated for levels (in tertiles) of maximum magnetic field exposure ≥16 mG. The association was stronger for early miscarriages (<10 weeks of gestation) (RR = 2.2, 95% CI = 1.2–4.0) and among “susceptible” women with multiple prior fetal losses or subfertility (RR = 3.1, 95% CI = 1.3–7.7). After excluding women who indicated that their daily activity pattern during the measurements did not represent their typical daily activity during pregnancy, the association was strengthened; RR = 2.9 (95% CI = 1.6–5.3) for maximum magnetic field exposure ≥16 mG, RR = 5.7 (95% CI = 2.1–15.7) for early miscarriage, and RR = 4.0 (95% CI = 1.4–11.5) among the susceptible women. Our findings provide strong prospective evidence that prenatal maximum magnetic field exposure above a certain level (possibly around 16 mG) may be associated with miscarriage risk. This observed association is unlikely to be due to uncontrolled biases or unmeasured confounders.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We conducted a nested case-control study (177 cases, 550 controls) to assess the relation between retrospective magnetic field measures and clinical miscarriage among members of the northern California Kaiser Permanente medical care system. We also conducted a prospective substudy of 219 participants of the same parent cohort to determine whether 12-week and 30-week exposure assessments were similar. We evaluated wire codes, area measures, and three personal meter metrics: (1) the average difference between consecutive levels (a rate-of-change metric), (2) the maximum level, and (3) the time-weighted average. For wire codes and area measures we found little association. For the personal metrics (30 weeks after last menstrual period), we found positive associations. Each exposure was divided into quartiles, with the lowest quartile as referent. Starting with the highest quartile, adjusted odds ratios and 95% confidence intervals were 3.1 (95% CI = 1.6–6.0), 2.3 (95% CI = 1.2–4.4), and 1.5 (95% CI = 0.8–3.1) for the rate-of-change metric; 2.3 (95% CI = 1.2–4.4), 1.9 (95% CI = 1.0–3.5), and 1.4 (95% CI = 0.7–2.8) for the maximum value; and 1.7 (95% CI = 0.9–3.3), 1.7 (95% CI = 0.9–3.3), and 1.7 (95% CI = 0.9–3.3) for the time-weighted average. The odds ratio conveyed by being above a 24-hour time-weighted average of 2 milligauss was 1.0 (95% CI = 0.5–2.1). Exposure assessment measurements at 12 weeks were poorly correlated with those taken at 30 weeks. Nonetheless, the prospective substudy results regarding miscarriage risk were consistent with the nested study results.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We evaluated the role of dietary vitamin C, vitamin E, and beta-carotene, as well as long-term vitamin E and beta-carotene supplementation, on the incidence of common cold episodes. A cohort of 21,796 male smokers was drawn from the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study, which examined the effects of 50 mg per day vitamin E and 20 mg per day beta-carotene on lung cancer. Diet and background characteristics were recorded at the study entry, and subjects were queried three times per year on common cold episodes. We modeled the total number of colds during a 4-year follow-up period with Poisson regression, adjusting for covariates of dietary intake. Dietary vitamins C and E and beta-carotene had no meaningful association with common cold incidence. Long-term vitamin E and beta-carotene supplementation had no overall effect.Among subjects 65 years of age or older, the incidence of colds was slightly lower in the vitamin E group (RR = 0.95; 95% CI = 0.90–1.00); this reduction was greatest among older city dwellers who smoked fewer than 15 cigarettes per day (RR = 0.72; 95% CI = 0.62–0.83). In this male smoking population, vitamins C and E and beta-carotene had no overall association with the incidence of common cold episodes.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

To examine whether intake of vitamin C and zinc is associated with a decrease in the risk of a common cold, we analyzed data from a cohort study carried out in a population of 4,272 faculty and staff from five Spanish universities. Participants were 21–65 years of age, were full-time workers at those universities, and did not have antecedents of asthma or chronic obstructive pulmonary disease. Daily intake of vitamin C and zinc was assessed at baseline by means of a food frequency questionnaire of which the validity and reproducibility were determined in a sample of the population. Subjects were traced for 1 year to detect episodes of common cold, the diagnosis of which was based on symptoms and was validated by additional clinical signs. We detected 1,667 cases of common cold in 79,240 person-weeks of follow-up. Intake of vitamin C and zinc was not related to the occurrence of common cold. Compared with the first quartile of intake, women in the fourth quartile of vitamin C intake showed an adjusted incidence rate ratio of 1.0 (95% CI = 0.7–1.3), and for zinc intake this figure was 1.1 (95% CI = 0.8–1.5). The incidence rate ratios for men in the fourth quartile were 1.1 (95% CI = 0.8–1.4) for vitamin C and 1.3 (95% CI = 0.9–1.8) for zinc.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

In studies of magnetic field exposure and childhood leukemia, power lines and other electrical installations close to the children’s homes constitute the most extensively studied source of exposure. We conducted a study to assess whether exposure to magnetic fields in infant incubators is associated with an increased leukemia risk. We identified all children with leukemia born in Sweden between 1973 and 1989 from the national Cancer Registry and selected at random one control per case, individually matched by sex and time of birth, from the study base. We retrieved information about treatment in infant incubators from medical records. We made measurements of the magnetic fields inside the incubators for each incubator model kept by the hospitals. Exposure assessment was based on measurements of the magnetic field level inside the incubator, as well as on the length of treatment. For acute lymphoblastic leukemia, the risk estimates were close to unity for all exposure definitions. For acute myeloid leukemia, we found a slightly elevated risk, but with wide confidence intervals and with no indication of dose response. Overall, our results give little evidence that exposure to magnetic fields inside infant incubators is associated with an increased risk of childhood leukemia.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We examined potential confounding factors that, if unaccounted for, could possibly produce a spurious association in a study of breast cancer among women occupationally exposed to magnetic fields. For each risk factor, we estimated strength of association, prevalence in the general population, and prevalence of the risk factor in the exposed group required to explain completely hypothetical odds ratios between occupational exposure to magnetic fields and breast cancer. We performed similar analyses for two, three, four, and five confounding factors acting simultaneously. Factors numerically capable of substantial confounding included obesity, continent of birth, family history of breast cancer in a first-degree relative, densities on the mammogram, benign proliferative breast disease, history of cancer in one breast, and consumption of at least two alcoholic drinks per day. Nevertheless, only continent of birth, history of cancer, obesity, and consumption of alcohol could potentially be related to occupation. Uncontrolled confounders, either alone or in combination, could possibly account for odds ratios in the 1.2–1.3 range but were very unlikely to produce an odds ratio of more than 1.5. A spurious negative association between magnetic fields and breast cancer could occur if the exposed group included a large number of immigrants from Asia and Africa.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We studied the fertility of the parents of 163 women with epithelial ovarian carcinoma in two hospitals in New York City, compared with the parents of 159 controls from similar neighborhoods. We used unconditional logistic regression to control for covariates, including parity, oral contraceptive use, age at menarche, and Jewish ancestry. Compared with women with zero or one sibling, those with two, three or four or more siblings had adjusted odds ratios (95% confidence intervals) of 0.91 (0.47–1.77), 0.61 (0.28–1.37), and 0.50 (0.26–0.98). On average, each additional sibling was associated with a risk reduction to 0.80 (0.66–0.98). These findings support the hypothesis that heritable conditions associated with reduced fertility of the subjects’ parents may contribute to risk and may explain some of the effects of parity on the risk of this carcinoma. Alternatively, they may reflect some unidentified aspect of the environment experienced by girls growing up in small families. If confirmed in other data sets, these findings imply that sibship size might have confounded previous estimates of risk associated with a family history of cancer or with Jewish ethnicity.

ISSN:1044-3983    

出版商:OVID    

年代:2002

数据来源: OVID