Summary
Objectives
To assess the effect of poor sleep quality on Overweight/Obesity (Ow/Ob) in young subjects, and explore if this association is independent of sleep duration.
Methods
Pubmed, ...EMBASE, and MEDLINE databases were searched for papers on sleep quality and overweight/obesity, focusing on children, adolescents, and young adults. Studies based on subjects with medical/psychological problems or published in languages other than English were excluded. Quality effects model was used to pool studies for meta‐analysis.
Results
Findings from the systematic review suggest a link between poor sleep quality and Ow/Ob in young subjects. Pooled estimate (from 26,553 subjects) suggest a role of inadequate sleep (including both short duration and poor quality) in Ow/Ob (OR: 1.27 95% CI: 1.05‐1.53). Sub‐group‐analyses suggest considerably higher odds of Ow/Ob (OR = 1.46, 95% CI: 1.24‐1.72) in young subjects with poor sleep quality (independent of duration).
Conclusions
Poor sleep quality seems to be associated with Ow/Ob, and some studies indicate this association to be independent of duration. Therefore, considering only sleep duration might not help in disentangling sleep‐obesity association. However, this review is mostly composed of cross‐sectional studies. Therefore, a causal link or the stability of the sleep quality and Ow/Ob association could not be established.
Short sleep duration is considered a potential risk for overweight/obesity in childhood and adolescence. However, most of the evidence on this topic is obtained from cross‐sectional studies; ...therefore, the nature and extent of the longitudinal associations are unclear. This study explores the prospective association between short sleep and overweight/obesity in young subjects. The MEDLINE, EMBASE, Pubmed, and CINAHL databases were searched for English‐language articles, published until May 2014, reporting longitudinal association between sleep and body mass index (BMI) in children and adolescents. Recommendations of the Sleep Health Foundation were used to standardize reference sleep duration. Sleep category, with sleep duration less than the reference sleep, was considered as the short sleep category. Meta‐analysis was conducted to explore the association between short sleep and overweight/obesity. A review of 22 longitudinal studies, with subjects from diverse backgrounds, suggested an inverse association between sleep duration and BMI. Meta‐analysis of 11 longitudinal studies, comprising 24,821 participants, revealed that subjects sleeping for short duration had twice the risk of being overweight/obese, compared with subjects sleeping for long duration (odds ratio 2.15; 95% confidence interval: 1.64–2.81). This study provides evidence that short sleep duration in young subjects is significantly associated with future overweight/obesity.
Gestational weight gain (GWG) is considered one of the risk factors for future obesity in the offspring. However, the direction and strength of this association at different periods of offspring life ...is relatively unknown. This study investigates whether excess or inadequate maternal GWG during pregnancy influences the risk of offspring obesity at different stages in life. A systematic review of published articles was undertaken after a comprehensive search of different databases, and extracted data were meta‐analysed. To quantify offspring obesity estimates in relation to GWG, we stratified obesity estimates within three life stages of the offspring age: <5 years, 5 to <18 years and 18+ years. Our meta‐analysis showed that, compared with offspring of women with adequate GWG, offspring of women who gained inadequate gestational weight were at a decreased risk of obesity (relative risk RR: 0.86; 95% confidence interval CI: 0.78–0.94), and offspring of women who gained excess weight were at an increased risk of obesity (RR: 1.40; 95% CI: 1.23–1.59). These relationships were similar after stratification by life stage. Findings of this study therefore suggest that excess GWG does influence offspring obesity over the short‐ and long‐term, and should therefore be avoided.
Gestational weight gain (GWG) is associated with postpartum weight retention (PPWR) in women. The strength of the association between GWG and long‐term PPWR and body mass index (BMI), however, is ...still unclear. Publications from different databases were systematically extracted and the articles relevant to this study were reviewed to quantify the effect estimate of GWG on PPWR and BMI using a bias‐adjusted method. The Institute of Medicine categories of “inadequate,” “adequate,” and “excess” were used to define GWG. The time span for PPWR was divided into three periods (<1 year, 1 year to 9 years, and ≥15 years) to determine outcome at different times postpartum. Twelve studies met the eligibility criteria and were included in the analyses. Women with an inadequate GWG had a significantly lower mean PPWR of −2.14 kg (95%CI, −2.61 to −1.66) than women with an adequate GWG, who had a mean PPWR of 3.15 kg (95%CI, 2.47 to 3.82) up to 21 years postpartum. Over the postpartum time span, a U‐shaped relationship was observed between the weighted mean difference calculated for women with excess GWG and the weighted mean difference calculated for women with adequate GWG, and this relationship was time independent between these two groups. Postpartum BMI showed a similar relationship and magnitude of change, but the exact loss or gain was difficult to assess due to fewer studies (n = 5) with considerable heterogeneity of BMI measurements. The findings of this study suggest that GWG outside of the Institute of Medicine recommendations can lead to both short‐term and long‐term postpartum weight imbalance.
The aim of the study was to investigate the effect of number of studies in a meta-analysis on the detection of publication bias using P value–driven methods.
The proportion of meta-analyses detected ...by Egger's, Harbord's, Peters', and Begg's tests to have asymmetry suggestive of publication bias were examined in 5,014 meta-analyses from Cochrane reviews. P values were also assessed in meta-analyses with varying number of studies, whereas symmetry was held constant. A simulation study was conducted to investigate if the above tests underestimate or overestimate the presence of publication bias.
The proportion of meta-analyses detected as asymmetrical via Egger's, Harbord's, Peters', and Begg's tests decreased by 42.6%, 41.1%, 29.3%, and 28.3%, respectively, when the median number of studies in the meta-analysis decreased from 87 to 14. P values decreased as the number of studies increased in the meta-analysis, despite the level of symmetry remaining constant. The simulation study confirmed that when publication bias is present, P value tests underestimate the presence of publication bias, particularly when study numbers are small.
P value–based tests used for the detection of publication bias–related asymmetry in meta-analysis require careful examination, as they underestimate asymmetry. Alternative methods not dependent on the number of studies are preferable.
The quality of primary research is commonly assessed before inclusion in meta-analyses. Findings are discussed in the context of the quality appraisal by categorizing studies according to risk of ...bias. The impact of appraised risk of bias on study outcomes is typically judged by the reader; however, several methods have been developed to quantify this risk of bias assessment and incorporate it into the pooled results of meta-analysis, a process known as bias adjustment. The advantages, potential limitations, and applicability of these methods are not well defined.
Comparative evaluation of the applicability of the various methods and their limitations are discussed using two examples from the literature. These methods include weighting, stratification, regression, use of empirically based prior distributions, and elicitation by experts.
Use of the two examples from the literature suggest that all methods provide similar adjustment. Methods differed mainly in applicability and limitations.
Bias adjustment is a feasible process in meta-analysis with several strategies currently available. Quality effects modelling was found to be easily implementable with fewer limitations in comparison to other methods.
The inconsistency demonstrated across strata when using different scales has been attributed to quality scores, and stratification continues to be done using risk of bias domain judgments. This study ...examines if restricting primary meta-analyses to studies at low risk of bias or presenting meta-analyses stratified according to risk of bias is indeed the right approach to explore potential methodological bias.
Reanalysis of the impact of quality subgroupings in an existing meta-analysis based on 25 different scales.
We demonstrate that quality stratification itself is the problem because it induces a spurious association between effect size and precision within stratum. Studies with larger effects or lesser precision tend to be of lower quality—a form of collider-stratification bias (stratum being the common effect of the reasons for these two outcomes) that leads to inconsistent results across scales. We also show that the extent of this association determines the variability in effect size and statistical significance across strata when conditioning on quality.
We conclude that stratification by quality leads to a form of selection bias (collider-stratification bias) and should be avoided. We demonstrate consistent results with an alternative method that includes all studies.
This study outlines the development of a new method (split component synthesis; SCS) for meta-analysis of diagnostic accuracy studies and assesses its performance against the commonly used bivariate ...random effects model.
The SCS method summarizes the study-specific diagnostic odds ratio (on the ln(DOR) scale), which mainly reflects test discrimination rather than threshold effects, and then splits the summary ln(DOR) into its component parts, logit sensitivity (Se) and logit specificity (Sp). Performance of SCS estimator was assessed through simulation and compared against the bivariate random effects model estimator in terms of bias, mean squared error (MSE), and coverage probability across varying degrees of between-studies heterogeneity.
The SCS estimator for the DOR, Se, and Sp was less biased and had smaller MSE than the bivariate model estimator. Despite the wider width of the 95% confidence intervals under the bivariate model, the latter had a poorer coverage probability than that under the SCS method.
The SCS estimator outperforms the bivariate model estimator and thus represents an improvement in the approach to diagnostic meta-analyses. The SCS method is available to researchers through the diagma module in Stata and the SCSmeta function in R.
•Meta-analyses of diagnostic studies are currently undertaken by synthesizing sensitivity (Se) and specificity (Sp) pairs and the bivariate linear mixed models are the most popular method for synthesis.•The Se/Sp pairs are components of the diagnostic odds ratio (DOR) but are threshold variant unlike the DOR and this study proposes that synthesis models should start from the DOR and then split this into its components.•Simulation demonstrates better performance of this method compared to the traditional bivariate approach.•Software is available to run this new method
We present a study of the sub-parsec scale radio structure of the radio galaxy 3C 84/NGC 1275 based on the Very Long Baseline Array data at 43 GHz. We discover a limb brightening in the "restarted" ...jet that is associated with the 2005 radio outburst. In the 1990s, the jet structure was ridge brightening rather than limb brightening, despite the observations being done with similar angular resolutions. This indicates that the transverse jet structure has recently changed. This change in the morphology reveals an interesting agreement with the gamma -ray flux increase, i.e., the gamma -ray flux in the 1990s was at least seven times lower than the current one. One plausible explanation for the limb brightening is that the velocity structure of the jet is in the context of the stratified jet, which is a successful scenario that explains the gamma -ray emission in some active galactic nuclei. If this is the case, then the change in apparent transverse structure might be caused by the change in the transverse velocity structure. We argue that the transition from ridge brightening to limb brightening is related to the gamma -ray time variability on the timescale of decades. We also discuss the collimation profile of the jet.
Summary Background Soil-transmitted helminth infections are a major global health issue, causing substantial morbidity in the world's poorest populations. Regular delivery of anthelmintic drugs is ...the mainstay for global soil-transmitted helminth control. Deworming campaigns are often targeted to school-aged children, who are at high risk of soil-transmitted-helminth-associated morbidity. However, findings from modelling studies suggest that deworming campaigns should be expanded community-wide for effective control of soil-transmitted helminth transmission. We aimed to do a systematic review and meta-analysis to compare the effect of mass (community-wide) and targeted (children only) anthelmintic delivery strategies on soil-transmitted helminth prevalence in school-aged children. Methods In this systematic review and meta-analysis, we searched MEDLINE, Embase, and Web of Science for articles published on or before Nov 5, 2015, reporting soil-transmitted helminth prevalence before and after distribution of albendazole or mebendazole, either targeted to children or delivered to the whole community. We excluded studies in which drug delivery was restricted to infected individuals or to a subset of the community or school, or if follow-up time was less than 3 months or greater than 18 months after drug delivery. We extracted data on study year, country, drug administration strategy, drug dose, number of deworming rounds, treatment coverage, diagnostic method, follow-up interval, and soil-transmitted helminth prevalence before and after treatment. We used inverse variance weighted generalised linear models, with prevalence reduction as the outcome variable, to examine the effect of mass versus targeted drug administration, as well as baseline prevalence, number of drug doses, and follow-up time. This study is registered with PROSPERO, number CRD42016026929. Findings Of 10 538 studies identified, 56 studies were eligible for the systematic review and 38 of these were included in meta-analysis. Results of the regression models showed that mass deworming led to a significantly greater reduction in prevalence in children than targeted deworming, for both hookworm (odds ratio 4·6, 95% CI 1·8–11·6; p=0·0020) and Ascaris lumbricoides (16·4, 2·1–125·8; p=0·0092), with no effect seen for Trichuris trichiura . There was significant heterogeneity across studies; for targeted studies I2 was 97% for A lumbricoides and hookworm, and 96% for T trichiura , and for mass studies, I2 was 89% for A lumbricoides , 49% for hookworm, and 66% for T trichiura. Interpretation The results of this meta-analysis suggest that expanding deworming programmes community-wide is likely to reduce the prevalence of soil-transmitted helminths in the high-risk group of school-aged children, which could lead to improved morbidity outcomes. These findings are in support of recent calls for re-evaluation of global soil-transmitted helminth control guidelines. Funding None.
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