ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We recruited 221 women with no known fertility problems who were discontinuing contraception to conceive a pregnancy. The primary objective of this prospective study was to estimate the incidence of very early pregnancy loss by using a highly sensitive and specific assay to detect the pregnancy hormone chorionic gonadotropin in first morning urine specimens. We found the risk of early pregnancy loss, defined as loss within 6 weeks of the last menstrual period, to vary by season of conception, with a large amplitude and some consistency across the 3 years of the study. Such a seasonal pattern may reflect the contribution of an environmental factor that varies with season. The peaks in risk ranged from early September to early December. A seasonal pattern of early pregnancy loss should contribute to a corresponding lagged seasonal pattern in livebirths. Accordingly, we looked for corroborative evidence in regional birth data from the same years. There was some correspondence, but this was largely limited to the first year of the study. (Epidemiology 1994;5:484–489)

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

To assess the impact of family planning status on maternal mortality, we analyzed data gathered in a community-based, maternal mortality surveillance study conducted by the Sichuan Health Department in the People's Republic of China during 1989–1991. The overall maternal mortality ratio, which included only deaths of pregnant women within family planning guidelines (“planned” pregnancies), was 78.9 per 100,000 livebirths. When the deaths of pregnant women outside of family planning (“unplanned” pregnancies) were included, the maternal mortality ratio doubled to 135.6 per 100,000 livebirths. The leading causes of death for women with “planned” and “unplanned” pregnancies were the same: hemorrhage, postpartum infection, pregnancy-induced hypertension, cardiac diseases, and pulmonary diseases. As among women with “planned” pregnancies, about 40% of maternal deaths among women with “unplanned” pregnancies occurred at home, and 20% occurred en route to a hospital. After controlling for the confounding effects of gravidity and education, the odds ratio of maternal death associated with “unplanned” pregnancy status was 2.6 [95% confidence interval (CI) = 2.0–3.7], which declined to 2.0 (95% CI = 1.4–2.9) with additional control for the effect of prenatal care visits. Our study indicates that women with “unplanned” pregnancies have a higher risk of maternal death, which is only partially attributed to less prenatal care. (Epidemiology 1994;5:490–494)

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We studied the associations between 11 scales of social functioning and risk of death over an average follow-up time of 71 months in 42− to 60-year-old men in the Kuopio Ischemic Heart Disease Risk Factor Study. In age-adjusted analyses, men were at increased risk of death if they reported few persons to whom they gave or received social support, nonparticipation in organizations, low quality of social relationships, a small number of friends, or not currently being married. Frequency of interaction, shyness, and use of emotional support when troubled were not associated with risk of death; the use of instrumental support when troubled was associated with increased risk. There was little evidence of confounding of these associations by the presence of 31 chronic or acute conditions, perceived health status, or six risk factors. Consistent associations were found in a healthy subgroup. These data add to the growing body of literature linking mortality risk with social functioning, especially in relation to organizational participation and quality of relationships. (Epidemiology 1994;5:495–500)

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We conducted a case-control study to test the hypothesis that exposure to magnetic fields of the type generated by high-voltage power lines increases the incidence of leukemia and central nervous system tumors in adults. The study was based on people who, between 1960 and 1985, had lived on a property in Sweden located within 300 meters of 220 or 400 kilovolt power lines. We identified a total of 325 leukemia cases and 223 cases of central nervous system tumor. Two matched controls per case were selected at random. We assessed exposure by spot measurements and by calculations of the magnetic fields generated by the power lines. For calculated magnetic field levels of 0.2 mUT or more closest in time to diagnosis, we found an elevated relative risk (RR) for acute myeloid leukemia [RR = 1.7; 95% confidence interval (CI) = 0.8–3.5] and chronic myeloid leukemia [RR = 1.7; 95% CI = 0.7–3.8]. Using cumulative exposure for the 15 years preceding diagnosis, we found relative risk estimates for acute and chronic myeloid leukemia of 2.3 (95% Cl = 1.0–4.6) and 2.1 (95% CI = 0.9–4.7), respectively, for the highest exposure category. For chronic lymphatic leukemia and for central nervous system tumors, relative risk estimates were close to or below unity. (Epidemiology 1994;5:501–509)

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Continuous exposure variables are frequently categorized in epidemiologic data analysis. It has recently been shown that such categorization may transform nondifferential error in measuring continuous exposure variables into differential exposure misclassification. This paper assesses the direction and magnitude of the resulting misclassification bias under a variety of practically relevant forms of nondifferential measurement error. The expected bias of measures of the exposure-disease association is toward the null in the case of purely random measurement error with a mean of zero. Systematic nondifferential over- or underestimation of the exposure may bias measures of the exposure-disease association either toward the null or away from the null, depending on the underlying distribution of exposure, the true exposure-disease relation, and the cutpoints employed for categorization. If exposure measurement error has both random and systematic components, the direction of the net bias is less predictable than with pure error of either type, but bias toward the null is increasingly likely as the random component grows larger. The results indicate the need for careful evaluation of potential effects of nondifferential exposure measurement error in epidemiologic studies in which categories are formed from continuous exposure variables. (Epidemiology 1994;5:510–517)

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Dietary assessment methods usually are validated one against the other, using the correlation coefficient between the methods to assess agreement. The correlation coefficient, however, is only an indicator of relative agreement and depends on the range of intakes. As this dependence can lead to misinterpretation, we propose that the standard deviation of the difference between methods should be used as an indicator of absolute agreement and the standard deviation of their average as an indicator of the range of intakes. We illustrate this method in a validation study of a diet history against a 3-day diet record in 58 non-insulindependent diabetes mellitus patients. A re-analysis of studies from the literature validating food frequency questionnaires against diet records showed that the absolute agreement between methods is very consistent and that the differences in the correlation coefficients are mostly due to the selection of subjects. (Epidemiology 1994;5:518–524)

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

There is some evidence that sex hormones may influence the incidence of rheumatoid arthritis. Obesity has been found to increase endogenous estrogens, particularly among postmenopausal women. Although the association of endogenous hormones with smoking and alcohol use is less clear, we examined the relation of these three factors with rheumatoid arthritis in women. We conducted a population-based case-control study of rheumatoid arthritis in King County, WA, and Group Health Cooperative of Puget Sound. We compared 349 incident cases of rheumatoid arthritis with 1,457 controls selected by random digit dialing or by random selection from the enrollment files of Group Health Cooperative. We conducted personal interviews to collect data on weight, smoking, alcohol history, reproductive variables, and other demographic variables. Women with 20 or more pack-years of smoking had a relative risk of 1.5 [95% confidence interval (CI) = 1.0–2.0] compared with never-smokers. Post-menopausal women who averaged more than 14 alcoholic drinks per week had a reduced risk of rheumatoid arthritis (relative risk = 0.5; 95% CI = 0.2–1.7). Women in the highest quartile of body mass index had a risk of 1.4 (95% CI = 1.0–2.0) relative to women with lowest body mass index. (Epidemiology 1994;5:525–532)

ISSN:1044-3983    

出版商:OVID    

年代:1994

数据来源: OVID