Reliability of proxy-reported and self-reported household appliance use

Potential health impacts of residential exposures to extremely low frequency magnetic fields in Europe

Over the last two decades residential exposure to extremely low frequency magnetic fields (ELF MF) has been associated with childhood leukaemia relatively consistently in epidemiological studies, though causality is still under investigation. We aimed to estimate the cases of childhood leukaemia that might be attributable to exposure to ELF MF in the European Union (EU27), if the associations seen in epidemiological studies were causal. We estimated distributions of ELF MF exposure using studies identified in the existing literature. Individual distributions of exposure were integrated using a probabilistic mixture distribution approach. Exposure-response functions were estimated from the most recently published pooled analysis of epidemiological data. Probabilistic simulation was used to estimate population attributable fractions (AFP) and attributable cases of childhood leukaemia in the EU27. By assigning the literature review-based exposure distribution to all EU27 countries, we estimated the total annual number of cases of leukaemia attributable to ELF MF at between ~50 (95% CIs: -14, 132) and ~60 (95% CIs: -9, 610), depending on whether exposure-response was modelled categorically or continuously, respectively, for a non-threshold effect. This corresponds to between ~1.5% and ~2.0% of all incident cases of childhood leukaemia occurring annually in the EU27. Considerable uncertainties are due to scarce data on exposure and the choice of exposure-response model, demonstrating the importance of further research into better understanding mechanisms of the potential association between ELF MF exposure and childhood leukaemia and the need for improved monitoring of residential exposures to ELF MF in Europe.

Do outcomes of acupuncture for back pain differ according to varying sociocultural contexts? The view from China

OBJECTIVES

What are the outcomes of acupuncture for back pain? According to well-regarded trials, acupuncture is little better for back pain than biomedicine, and active acupuncture is no better than sham acupuncture. These trials occurred in the West. Patients are inside the clinic a miniscule amount of time in relation to the time they are outside the clinic and enmeshed in the wider sociocultural context. Nevertheless, trials have largely overlooked potential effects of sociocultural context. The main objective of this article is to draw attention to designated features of sociocultural context that, as compared with outcomes obtained in the West, may enhance outcomes of acupuncture for back pain in China. Additional objectives of the article are to reconceptualize "sociocultural context" so that it is measurable, and to measure pre-existing acquaintance with acupuncture and other forms of Traditional Chinese Medicine (TCM) within the sociocultural context of China.

DESIGN/SETTING/SUBJECTS

Back pain patients (N=86) were recruited from the Acupuncture Clinic and Pain Clinic of West China Hospital (Chengdu, Sichuan Province). Patients completed questionnaires on their use of TCM before they came to the Acupuncture Clinic and their families' use of TCM.

RESULTS

Most patients had used TCM, and those who did so likely used it repeatedly, which indicated substantial acquaintance with TCM beliefs in the cultural context. Patients whose families used TCM were also likely to use it themselves, which indicated that TCM use was anchored in the social context of the family.

CONCLUSIONS

Although multiple studies substantiate biologic mechanisms of acupuncture, there is not necessarily a fixed relationship between those mechanisms and people's experience of them. Rather, sociocultural context may interact with biologic mechanisms and mediate this experience. The theory proposed here explains why outcomes of acupuncture for back pain will potentially be more pronounced in the sociocultural context of China than in the West.

Exploring exposure--response for magnetic fields and childhood leukemia

For 30 years, there have been suggestions that extremely low frequency magnetic fields such as those are produced by electric power systems may be associated with elevated risks of childhood leukemia. These suggestions are driven by epidemiological evidence, and it has been common to characterize that evidence as showing a threshold effect, with no increase in risk below a threshold, often 0.3 or 0.4 μT, and a constant risk above it. Such a threshold would, however, be biologically unlikely. We tested alternative dose-response relationships quantitatively. We obtained five exposure data sets, applied several candidate dose-response relationships to each one, and performed a regression analysis to see how well they fit each of the three epidemiological data sets. Threshold dose-response relationships performed only moderately. Linear relationships were generally even poorer. The fit was improved by adding quadratic terms or performing non-linear regression. There are limitations in our analysis, stemming from the available data, but addressing this issue in a data-based, quantitative manner should improve understanding, allow better calculations to be made of attributable numbers, and hence ultimately inform public policy making.

Completeness and utility of interview data from proxy respondents in prenatal care research in rural China

In household surveys, the use of data provided by relatives can increase response rates and generalisability of research findings. This study assessed the quality of data from relatives and the impact of the data source on the association between the use of prenatal care and pregnancy outcomes. Data for 3,673 new mothers and 293 proxy respondents were available from a house-hold survey in 2008-2009 in rural China. Analyses were performed using chi-square test, ANOVA, Kruskal-Wallis test, and logistic regression models. Differences in the studied variables were small, but proxy respondents were slightly more likely to have missing data than the new mothers. Differences and missing data were more common for the use of prenatal care and outcome variables (mode of delivery, place of delivery, birth weight, use of postnatal care, and gestational age at birth) than for the background characteristics of the participants. Husbands' reports were closer to the index reports than that of the other proxies. The associations between the exposures and outcomes were mostly similar between the proxy and index respondents. Relatives can be interviewed instead of women to study prenatal care without a substantial negative impact on study results. Studies using proxy respondents should stratify the analysis by type of respondents.

Reliability of self-reported reproductive factors and childhood social class indicators in a case-control study in women

PURPOSE

Reproductive factors are often evaluated in epidemiologic interview studies as risk factors for diseases in women. Similarly, childhood social class has been implicated in the etiology of several diseases. Nevertheless, questions related to these factors have not been thoroughly evaluated for test-retest reliability. This research measured the test-retest reliability of reproductive and childhood social class variables, and determined whether reliability differed by case-control status, age, educational level, time between interviews, and interviewer-rated quality of the interview.

METHODS

Subjects were participants in a population-based case-control in-person interview study of Hodgkin's disease in northern California women. Twenty-four cases and 22 controls were reinterviewed by telephone between 1992 and 1995, with an average interval of 8 months between interviews. Reliability was assessed using kappa or intraclass correlation coefficients; mean reliability coefficients and 95% confidence intervals (CIs) were estimated using the bootstrap method.

RESULTS

Reliability was excellent for all variables (reliability coefficients between 0.76 and 0.96) and did not differ by case-control status (mean reliability = 0.82 for cases and 0.84 for controls), age (mean reliability = 0.85 for age < 40 and 0.82 for age > or = 40), time between interviews (mean reliability = 0.75 for 0-5 months, 0.88 for 6-11 months, and 0.87 for 1 year or more), or interviewer-rated quality of the validity of the original responses (mean reliability = 0.93 for "not too confident" and 0.83 for "confident"). However, reliability was consistently lower among less educated women (mean reliability = 0.56 for high school or less and 0.88 for more than high school), a finding consistent with results of prior studies.

CONCLUSIONS

These results indicate that questions about reproductive experience and childhood social class posed in in-person interviews can be answered reliably. However, inclusion of subjects at lower socioeconomic status may result in lower reliability for some interview responses.