1,721,099 research outputs found
A systematic review and dose-response meta-analysis of exposure to environmental selenium and the risk of type 2 diabetes in nonexperimental studies
No full textAccumulating evidence from both experimental and nonexperimental human studies in the last 15 years indicates that exposure to high levels of the trace element selenium increases the risk of type 2 diabetes. However, the relation of dose to effect is not well understood because randomized controlled trials used only one dose (200 mug/day) of selenium supplementation. While no new trial on this topic has been published since 2018, several nonexperimental studies have appeared. We therefore updated a previous meta-analysis to include recently published observational studies, and incorporated the recently developed one-stage random-effects model to display the dose-response relation between selenium and diabetes. We retrieved 34 potentially eligible nonexperimental studies on selenium and diabetes risk up to April 15, 2021. The bulk of the evidence indicates a direct relation between blood, dietary and urinary levels of selenium and risk of diabetes, but not with nail selenium, which is considered a less reliable biomarker. The association was nonlinear, with risk increasing above 80 mug/day of dietary selenium. Whole blood/plasma/serum selenium concentrations of 160 mug/L corresponded to a risk ratio of 1.96 (95% CI 1.27-3.03) compared with a concentration of 90 mug/L (approximately 60 mug of daily selenium intake). The cohort studies, which are less susceptible to reverse causation bias, indicated increased risk for both blood and urine selenium levels and dietary selenium intake, whereas no such pattern emerged from studies relying on nail selenium content. Overall, the nonexperimental studies agree with findings from randomized controlled trials, indicating that moderate to high levels of selenium exposure are associated with increased risk for type 2 diabetes
Selenium exposure and the risk of type 2 diabetes: a systematic review and meta-analysis
No full textIn 2007, supplementation with the trace element selenium in a trial was unexpectedly found to be associated with an excess risk of type 2 diabetes. Given the concerns raised by these findings and the large number of recent studies on this topic, we reviewed the available literature with respect to this possible association. In this paper, we assessed the results of both experimental and nonexperimental epidemiologic studies linking selenium with type 2 diabetes incidence. Through a systematic literature search, we retrieved 50 potentially eligible nonexperimental studies and 5 randomized controlled trials published through June 11, 2018. To elucidate the possible dose-response relation, we selected for further analysis those studies that included multiple exposure levels and serum or plasma levels. We computed a pooled summary risk ratio (RR) of diabetes according to selenium exposure in these studies. We also computed a RR for diabetes incidence following supplementation with 200 μg/day of selenium compared with placebo in trials. In the nonexperimental studies, we found a direct relation between selenium exposure and risk of diabetes, with a clear and roughly linear trend in subjects with higher plasma or serum selenium levels, with RR at 140 μg/L of selenium exposure compared with a referent category of < 45 μg/L equal to 3.6 [95% confidence interval (CI) 1.4-9.4]. A dose-response meta-analysis focusing on studies with direct assessment of dietary selenium intake showed a similar trend. In experimental studies, selenium supplementation increased the risk of diabetes by 11% (RR 1.11, 95% CI 1.01-1.22) compared with the placebo-allocated participants, with a higher RR in women than in men. Overall, results from both nonexperimental and experimental studies indicate that selenium may increase the risk of type 2 diabetes across a wide range of exposure levels. The relative increase in risk is small but of possible public health importance because of the high incidence of diabetes and the ubiquity of selenium exposure
Dietary cadmium intake and fecundability in a North American preconception cohort study
Get PDFObjective
To evaluate the association between dietary cadmium intake (D-Cd) and fecundability. Diet is one of the main sources of cadmium, and D-Cd is often used as indicator of cadmium exposure, particularly in non-smoking populations. In a previous preconception cohort study of 501 couples,1 high female cadmium concentrations measured in whole blood were associated with reduced fecundability.
Design
Prospective cohort study (2013-2018).
Materials and Methods
Pregnancy Online Study (PRESTO) is a North American prospective preconception cohort of pregnancy planners. At baseline, female participants aged 21-45 years completed a web-based questionnaire on demographic, lifestyle, medical and reproductive factors. Ten days after enrollment, participants completed the National Cancer Institute Dietary History Questionnaire II, a validated food frequency questionnaire (FFQ) of average intake during the previous year. D-Cd (μg/day) was estimated by combining FFQ responses with US Food and Drug Administration data on food cadmium content. Participants were then followed for up to 12 months or until reported pregnancy, whichever came first. The analysis included 4,768 women attempting to conceive for ≤6 cycles at study entry and not using fertility treatment. We used a proportional probabilities regression model to estimate fecundability ratios (FR) and 95% confidence intervals (CI), adjusted for age, body mass index (BMI), smoking history, parity, physical activity, last method of contraception, daily use of multivitamins, race/ethnicity, education, income, geographic region, and the 2010 healthy eating index score. We used the nutrient residual approach to adjust for energy intake.
Results
Median D-Cd was 8.0 μg/day (interquartile range: 7.0-9.1 μg/day). The top 5 contributors to D-Cd were nuts and seeds; fried potatoes; dark green lettuce; cooked greens; and white potatoes. Compared with an average D-Cd of <6.8 μg/day, FRs for D-Cd quintiles of 6.8-7.6, 7.7-8.4, 8.5-9.5, and ≥9.6 μg/day were 1.03 (CI: 0.92-1.14), 1.07 (CI: 0.96-1.18), 1.07 (CI: 0.96-1.19), and 1.08 (0.97-1.20), respectively. Results were not appreciably different among never smokers with no current passive smoke exposure, for whom cadmium exposure from other sources (e.g., cigarettes) would be lower (respective FRs: 1.02, 1.05, 1.06 and 1.02). Results did not differ materially by age (<30 vs. ≥30 years), BMI (<30 vs. ≥30 kg/m2), total fiber intake (<25 vs. ≥25 g/day), geographic region of residence (West, Midwest, Northeast, South, Canada), or attempt time at study entry (<3 vs. ≥3 cycles).
Conclusions
Dietary intake of cadmium was not appreciably associated with fecundability, though exposure misclassification and confounding could explain the null results.
References
1 Buck Louis GM, Sundaram R, Schisterman EF, Sweeney AM, Lynch CD, Gore-Langton RE, Chen Z, Kim S, Caldwell KL, Barr DB. Heavy metals and couple fecundity, the LIFE Study. Chemosphere. 2012 Jun;87(11):1201-7. https://doi.org/10.1016/j.chemosphere.2012.01.017. Epub 2012 Feb 4. PubMed PMID: 22309709; PubMed Central PMCID: PMC3327819
Exploration of structural and statistical biases in the application of propensity score matching to pharmacoepidemiologic data
Get PDFCertain pitfalls associated with propensity score matching have come to light, recently. The extent to which these pitfalls might threaten validity and precision in pharmacoepidemiologic research, for which propensity score matching often is used, is uncertain. We evaluated the “propensity score matching paradox” – the tendency for covariate imbalance to increase in a propensity score-matched dataset upon continuous pruning of matched sets – as well as the utility of coarsened exact matching, a technique that has been posed as a preferable alternative to propensity score matching, especially in light of the “propensity score matching paradox”. We show that the “propensity score matching paradox” may not threaten causal inference that is based on propensity score matching in typical pharmacoepidemiologic settings to the extent predicted by previous research. Moreover, even though coarsened exact matching substantially improves covariate balance, it may not be optimal in typical pharmacoepidemiologic settings due to the extreme loss of study size (and resulting increase in bias and variance) that may be required to build the matched dataset. Finally, we explain variability in 1:1 propensity score matching without replacement as well as methods that were developed to account for this variability, with application of these methods to an example claims-based study.2021-06-03T00:00:00
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Lockdown timing and efficacy in controlling COVID-19 using mobile phone tracking
Get PDFBackground
Italy's severe COVID-19 outbreak was addressed by a lockdown that gradually increased in space, time and intensity. The effectiveness of the lockdown has not been precisely assessed with respect to the intensity of mobility restriction and the time until the outbreak receded.
Methods
We used processed mobile phone tracking data to measure mobility restriction, and related those data to the number of new SARS-CoV-2 positive cases detected on a daily base in the three most affected Italian regions, Lombardy, Veneto and Emilia-Romagna, from February 1 through April 6, 2020, when two subsequent lockdowns with increasing intensity were implemented by the Italian government.
Findings
During the study period, mobility restriction was inversely related to the daily number of newly diagnosed SARS-CoV-2 positive cases only after the second, more effective lockdown, with a peak in the curve of diagnosed cases of infection occurring 14 to 18 days from lockdown in the three regions and 9 to 25 days in the included provinces. An effective reduction in transmission must have occurred nearly immediately after the tighter lockdown, given the lag time of around 10 days from asymptomatic infection to diagnosis. The period from lockdown to peak was shorter in the areas with the highest prevalence of the infection. This effect was seen within slightly more than one week in the most severely affected areas.
Interpretation
It appears that the less rigid lockdown led to an insufficient decrease in mobility to reverse an outbreak such as COVID-19. With a tighter lockdown, mobility decreased enough to bring down transmission promptly below the level needed to sustain the epidemic.
Funding
No funding sources have been used for this work
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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