Assessing the possible direct effect of birth weight on childhood blood pressure : a sensitivity analysis.

To estimate the possible direct effect of birth weight on blood pressure, it is conventional to condition on the mediator, current weight. Such conditioning can induce bias. Our aim was to assess the potential biasing effect of U, an unmeasured common cause of current weight and blood pressure, on the estimate of the controlled direct effect of birth weight on blood pressure, with the help of sensitivity analyses. We used data from a school-based study conducted in Switzerland in 2005-2006 (n = 3,762; mean age = 12.3 years). A small negative association was observed between birth weight and systolic blood pressure (linear regression coefficient βbw = -0.3 mmHg/kg, 95% confidence interval: -0.9, 0.3). The association was strengthened upon adjustment for current weight (βbw|C = -1.5 mmHg/kg, 95% confidence interval: -2.1, -0.9). Sensitivity analyses revealed that the negative conditional association was explained by U only if U was relatively strongly associated with blood pressure and if there was a large difference in the prevalence of U between low-birth weight and normal-birth weight children. This weakens the hypothesis that the negative relationship between birth weight and blood pressure arises only from collider-stratification bias induced by conditioning on current weight

Cost-Effective Screening for Breast Cancer Worldwide: Current State and Future Directions

Affordability of healthcare is highly limited by its skyrocketing cost. Access to screening and diagnostic medical equipment and medicine in developing countries is inadequate for the majority of the population. There is a tremendous worldwide need to detect breast cancer at its earliest stage. These needs must be balanced by the ability of countries to provide breast cancer screening technology to their populations. We reviewed the diagnostic accuracy, procedure cost and cost-effectiveness of currently available technique for breast screening and diagnosis including clinical breast examination, mammography, ultrasound, magnetic resonance imaging, biopsy and a new modality for cancer diagnostics termed elasticity imaging that has emerged in the last decade. Clinical results demonstrate that elasticity imaging even in its simplest and least sophisticated versions, like tactile imaging, has significant diagnostic potential comparable and exceeding that of conventional imaging techniques. In view of many countries with limited resources, effective yet less expensive modes of screening must be considered worldwide. The tactile imaging is one method that has the potential to provide cost-effective breast cancer screening and diagnostics

Looking back on 'Causal Thinking in the Health Sciences'

It has now been over a quarter of a century since the publication of Mervyn Susser's Causal Thinking in the Health Sciences (1973, Oxford University Press), the first book-length treatment of causal reasoning and inference in our field. Major contributions of this work were its holistic focus on the origins of health outcomes in the context of ecologic systems and its invigoration of the literature on causal criteria in epidemiology. Although a recent resurgence of interest in social context has revivified many points made by Susser, a formal basis for causal analysis consistent with this ecologic perspective has failed to emerge in public health research. Susser's discussion of causal criteria, on the other hand, helped spur a vigorous dialogue that has persisted unabated to the present day. Although the basic outline of the criteria has evolved little, their applications, interrelations, and relative contributions to causal judgments have been the subject of continued and sometimes contentious debate

Racial differences in blood pressure response to calcium channel blocker monotherapy: A meta-analysis

Background A systematic literature review was conducted to determine whether US blacks and whites have differential blood pressure (BP) response to calcium channel blocker (CCB) monotherapy.MethodsSix published studies made up the final cohort of eligible articles. Multiple treatment groups within some studies led to a total of eight sets of estimates for BP reduction with a total of 6,851 white or nonblack participants and 3,371 black participants.ResultsThe pooled difference in systolic blood pressure (SBP) change between blacks and whites was 2.7 mm Hg (95% confidence interval (CI): 4.0, 1.3) with blacks having greater response. The difference in diastolic blood pressure (DBP) between blacks and whites was 0.4 mm Hg (95% CI: 1.0, 0.3) with blacks having greater response. Using a dichotomous outcome measure, whites were found to be just as likely as blacks to attain the DBP goal of 90 mm Hg or a 10 mm Hg or greater change (relative risk: 1.00 95% CI: 0.91, 1.11). In addition, examination of the continuous distribution of BP responses of whites and blacks showed over 90% overlap in treatment response.ConclusionAssessment of differential response to CCB monotherapy by race in published data depends on choice of outcome metric. Nonetheless, the results of this systematic review indicate that BP response is qualitatively similar in US blacks and whites, suggesting that patient race is not likely to offer any clinical utility for decisions about the likely effect of this antihypertensive therapy

Neighborhood Deprivation and Adverse Birth Outcomes among Diverse Ethnic Groups

Living in a socioeconomically deprived neighborhood has been associated with an increased risk of adverse birth outcomes. However, variation in the effect of neighborhood deprivation among diverse ethnic groups has not been studied

Inverse Probability Weights for the Analysis of Polytomous Outcomes

Polytomous outcomes are common in epidemiologic studies. Analyses based on multinomial models employ a likelihood that utilizes the data observed in all outcome categories simultaneously and permits inferences regarding associations across outcome categories. However, the potentially large number of estimated parameters produced by multinomial model fitting can lead to problems of estimation and inference (1). We have proposed an inverse-probability-of-exposure weighted multinomial model for analysis of polytomous outcomes, described its implementation, and illustrated it. The approach yields marginal estimates of associations, which are sometimes desirable as summary measures of association (2). This approach allows for confounding control and tends to be less susceptible to problems of estimation that arise when at least one outcome category is rare

Probing the high momentum component of the deuteron at high Q^2

The d(e,e'p) cross section at a momentum transfer of 3.5 (GeV/c)^2 was measured over a kinematical range that made it possible to study this reaction for a set of fixed missing momenta as a function of the neutron recoil angle theta_nq and to extract missing momentum distributions for fixed values of theta_nq up to 0.55 GeV/c. In the region of 35 (deg) <= theta_nq <= 45 (deg) recent calculations, which predict that final state interactions are small, agree reasonably well with the experimental data. Therefore these experimental reduced cross sections provide direct access to the high momentum component of the deuteron momentum distribution in exclusive deuteron electro-disintegration.Comment: 5 pages, 2 figure