Linear Random Effects Models Research Articles

Assessing the relationship between left ventricular diastolic and systolic function during exercise in healthy volunteers using a novel individualised stress echocardiography protocol

Abstract Background Exercise stress echocardiography (ESE) provides a non-invasive estimation of diastolic function during exercise and can provide insight into systolic-diastolic coupling response. Current protocols are confounded by individual variation in fitness and exercise tolerance, which in turn leads to ESE normative data being difficult to define. Aims This study aims to use ESE to describe the relationship between diastolic and systolic left ventricular function in healthy volunteers using physiologically defined personalised exercise intensity domains, accounting for individual HR response, exercise intensity and cardiorespiratory fitness. Methods Participants underwent resting echocardiography, then a maximal CPET followed by ESE consisting of two 6-minute stages: 1; Moderate intensity (M-Int) at 90% of the work rate at the gas exchange threshold (GET) and 2; High intensity (H-Int) at 40% of the difference between GET and peak exercise. Average (septal and lateral) peak systolic (LV-S’) and diastolic (LV-E’) longitudinal annular velocities as well as early diastolic mitral inflow velocity (E) were measured. E/E’ ratio was calculated to estimate LV diastolic filling pressure. Physical activity (PA) levels were assessed using age-appropriate questionnaires. Random effects linear mixed models were used to analyse exercise test data. Results A total of 101 healthy children and adults (mean age 37.8 ± 15.7 years, range 9-65, male 48.5%) were included. Participants’ PA was low in 13%, moderate in 54% and high in 33% and mean peak VO2 was 36.1 ± 7.7 ml/min/kg (range 21.3 to 60.2). LV-S’ increased significantly between rest, M-Int and H-Int, while E/E’ ratio remained constant, after adjusting for heart rate (Figure 1A and B). There was a significant inverse relationship between E/E’ ratio and LV-S’ at rest (b: -0.39, p<0.001), M-Int (b: -0.7, p=0.007) and H-Int (b: -0.65, p=0.03), shown in Figure 2. When adjusted by exercise intensity, HR, age, gender, PA levels and peak VO2, this relationship remained statistically significant for M-Int (b: -0.42, p=0.02) and H-Int, (b: -0.71, p<0.001) but not for rest (b: -0.01, p=0.9). In addition to E/E’ ratio, other factors associated with LV-S’ change during exercise were HR, age, gender and peak VO2 (p<0.1 for all). Older age was associated with overall higher E/E' values (main effect 0.04/year) but not higher relative changes during exercise (interaction with Rest: p<0.001, M-Int: p=0.7, H-Int: p=0.5). Conclusion This study shows dynamic changes in systolic-diastolic coupling during exercise, in healthy volunteers, not present at rest. Systolic-diastolic coupling could provide insight into pathological exercise limiting mechanisms, such as in heart failure with preserved ejection fraction. A sub-maximal individualised ESE protocol can be a useful tool to assess this physiological mechanism, without the bias of individual variation in cardiorespiratory fitness affecting current protocols. Figure 1 Figure 2

Methylphenidate and Atomoxetine in Pregnancy and Possible Adverse Fetal Outcomes

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common neurobehavioral disorders, and it afflicts about 7% of young people. As a consequence, many young women might be pregnant while taking medication for ADHD, but data about safety have not yet been strictly examined. To examine adverse effects in offspring of mothers receiving treatment with atomoxetine and methylphenidate during pregnancy. Electronic databases (PubMed, Embase, and PsycINFO) were searched for articles published through December 31, 2023, with the following search terms: (atomoxetine OR methylphenidate) AND (pregnancy). Observational studies (eg, cohort studies, case-control studies, case-crossover studies, cross-sectional studies, and registry-based studies) that reported offspring outcomes in pregnancy with atomoxetine and/or methylphenidate and in mothers with ADHD but unexposed to ADHD treatment during pregnancy or from the general population were included. Ten studies of 656 records satisfied criteria. Two independent reviewers performed data extraction according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Meta-analyses were conducted based on reported odds ratios (ORs) and corresponding 95% CIs using a linear random effects model. Each study was inversely weighted by the reported variance of the estimators. Risk of publication bias and analysis of heterogeneity through univariate and multivariate metaregressions were also rated. Data were analyzed from January to March 2024. Study outcomes included miscarriages and congenital anomalies. Ten studies involving 16 621 481 pregnant women, 30 830 of them affected by ADHD, were included. Congenital anomalies or miscarriages were not more frequent in offspring of mothers receiving treatment with methylphenidate or atomoxetine during pregnancy compared with unexposed offspring (OR, 1.14; 95% CI, 0.83-1.55; P = .41; I2 = 8% for congenital anomalies; OR, 1.01; 95% CI, 0.70-1.47; P = .96; I2 = 0% for miscarriages) or compared with the general population (OR, 1.19; 95% CI, 0.93-1.53; P = .16; I2 = 74% for congenital anomalies; OR, 1.05, 95% CI, 0.81-1.37; P = .70; I2 = 0% for miscarriage). Evidence from this meta-analysis, which involves a substantial sample of pregnant women with and without ADHD, suggests the maintenance of methylphenidate or atomoxetine during pregnancy is safe, given that congenital anomalies and miscarriages did not appear to significantly increase. Further studies are recommended to support and confirm these findings.

Statistical modelling of growth curve for longitudinal data on a feeding trial in goat breeds

The growth curve parameters were estimated extending a linear regression to higher degree polynomial with attempts to use also the biologically appealing Gombertz function. The data contained monthly weight records from weaning to the age of 14 months of kids in two Omani goat breeds Sahrawi and Jabbali used in a feeding trial assessing the effect of concentrate supplement (14% crude protein). The growth curve parameters were estimated within the fixed effects breed and feed concentrate level (2 or 3% of live body weight) with an extension to mixed models using animals as random effects. The parameters and model contrasting were performed with ML or REML as appropriate with relative comparison relying on AIC and significance testing of estimated parameters. The mixed model analyses were performed with publicly available R software package programs. The fixed effect cubic regression with linear random effect model fitted into the data. The higher level of concentrates improved the immediate post-weaning growth in the same way in the breeds while the subsequent growth curve differed with more pronounced weight increments in the Jabbali breed.

Physical Activity Behaviour and Motivation During and Following Pulmonary and Cardiac Rehabilitation: A Repeated Measures Study.

Exercise rehabilitation programmes are important for long-term health and wellbeing among people with cardiac and pulmonary diseases. Despite this, many people struggle to maintain their physical activity once rehabilitation ends. This repeated measures study tracked changes in physical activity behaviour and motivation during and after completing a community-based exercise rehabilitation programme. Cardiac and pulmonary exercise rehabilitation patients (N = 31) completed six once-monthly measures of physical activity (MET·min), self-determined motivation, intention, and habit strength for rehabilitation exercise (within rehabilitation sessions) and lifestyle physical activity (outside of rehabilitation sessions). Linear regression and random effects models with estimated marginal means were used to test for associations between physical activity motivation and behaviour and change during and post-rehabilitation. Overall physical activity decreased after rehabilitation (823 MET·min) despite patients becoming more self-determined for lifestyle physical activity during rehabilitation. More self-determined motivation, stronger intentions, and stronger habits were associated with more lifestyle physical activity behaviour. However, none of these motivation variables were significantly associated with rehabilitation exercise behaviour. Among community-based cardiac and pulmonary rehabilitation patients, physical activity levels decreased following exercise rehabilitation programmes. The findings revealed clear distinctions in the motivation of rehabilitation exercise compared to lifestyle physical activity. Exercise rehabilitation programmes might improve the longevity of outcomes by integrating approaches to enhance lifestyle physical activity beyond the clinic.

Older parents’ perceptions of children's filial piety in rural China: The roles of coresidence, geographic proximity, and intergenerational support

Filial piety—the belief that children should provide care, support, respect, and obedience to their older parents—is a fundamental normative expectation in East Asian societies. This study investigates the relationship between the geographic proximity of children and the support received from them, and their parents’ perceptions of filial piety in rural China. We used the 2021 wave of the Longitudinal Study of Older Adults in Anhui Province to predict parental assessments of filial piety for each of their children. Random-effects linear probability models using an internal moderator approach were employed to compare coresident children with non-coresident children based on their proximity and support provided. Findings indicate that parents tend to perceive their coresident children as being more filial compared to non-coresident children, particularly when parents are in worse functional health. However, non-coresident children can compensate for their deficiency in being perceived as filial by providing more financial support and maintaining frequent telephone communication with their parents. The study's results suggest that filial piety norms in rural China have adapted to the diminished emphasis on intergenerational coresidence resulting from the trends of urbanization and significant rural–urban migration in modern China, requiring that children find alternative ways to fulfill their filial obligations.

Adverse childhood experiences and cancer: A systematic review and meta-analysis.

10565 Background: Cancer is one of the leading causes of morbidity and mortality globally, with increasing incidence rates. The major governing cancer societies identify cancer risk factors into five broad groups (infectious disease, environmental/chemical pollutants, genetics, behavioral and ultraviolet radiation). However, little attention has been dedicated to understanding the potential primordial risk of the early psychosocial environment. Life course epidemiology is a framework that considers how the harmful effects of adverse childhood experiences (ACEs) contribute to the development of disease later in life. It is postulated that such stressful events that occur during a critical period of development likely trigger increased inflammatory responses, which could ultimately contribute to the manifestation of chronic diseases such as cancer. While there are studies that have reported an association between ACEs and cancer, this relationship has yet to be systematically analyzed. The objectives of this study are to a) meta-analyze the pooled association of the presence of at least one ACE, b) the burden of different ACEs, and c) specific ACE types, and their association with cancer in adulthood. Methods: This systematic review compiled studies from PubMed, EMBASE, Medline, Web of Science, Google Scholar, Biological Psychiatry, and grey literature up to Mar 16, 2023, and was registered on PROSPERO. Observational studies with a comparator group that assessed ACEs that occurred prior to age 18, and diagnosed cancer ≥21 years of age were included. Two review authors independently screened articles, extracted data, assessed risk of bias using QUIPS, and conducted GRADE assessment. Pooled odds ratios (ORs) were calculated using multilevel linear random-effects models. Results: Of the total 39,658 articles, our search identified 26 studies, of which 23 studies (356,519 participants, 9 countries) were eligible for meta-analysis. The occurrence of ≥1 ACE(s) was associated with cancer (OR=1.16, 95% CI: 1.08-1.24, I2 = 58.7%), compared to participants with no ACEs. As the number of ACEs increased, the odds of cancer increased (≥4 ACEs compared to no ACEs OR=1.30, 1.04-1.62, p-trend = 0.0003). Specific ACE types did explain a significant amount of heterogeneity (F = 2.02, p = 0.04). Parental or sibling death (OR=1.88, 1.29-2.73), household mental illness (OR=1.36, 1.14-1.61), sexual abuse (OR=1.20, 1.04-1.37), and physical abuse (OR=1.18, 1.05-1.34) had the largest associations with cancer. Conclusions: Our findings confirm ACEs as important risk factors for cancer in adulthood. These findings have important clinical and public health implications to develop primary and secondary prevention and treatment strategies. Also, further research is warranted to explore this relationship on the epigenetic level, and among specific cancers.

Evaluation of DNA yield from various tissue and sampling sources for use in single nucleotide polymorphism panels

Genetics studies are used by wildlife managers and researchers to gain inference into a population of a species of interest. To gain these insights, microsatellites have been the primary method; however, there currently is a shift from microsatellites to single nucleotide polymorphisms (SNPs). With the different DNA requirements between microsatellites and SNPs, an investigation into which samples can provide adequate DNA yield is warranted. Using samples that were collected from previous genetic projects from regions in the USA from 2014 to 2021, we investigated the DNA yield of eight sample categories to gain insights into which provided adequate DNA to be used in ddRADseq or already developed high- or medium-density SNP panels. We found seven sample categories that met the DNA requirements for use in all three panels, and one sample category that did not meet any of the three panels requirements; however, DNA integrity was highly variable and not all sample categories that met panel DNA requirements could be considered high quality DNA. Additionally, we used linear random-effects models to determine which covariates would have the greatest influence on DNA yield. We determined that all covariates (tissue type, storage method, preservative, DNA quality, time until DNA extraction and time after DNA extraction) could influence DNA yield.

How much do conservation cropping practices mitigate runoff and soil erosion under Western European conditions: A focus on conservation tillage, tied ridging and winter cover crops

AbstractConservation farming practices are known for their capacity to mitigate runoff and erosion, but the magnitude of their effectiveness is highly variable across studies. In order to better understand the contribution of environmental and management factors to their effectiveness, up to 37 studies reporting 271 individual trials were collated for a quantitative review regarding 3 common conservation agriculture‐related practices, at the plot scale and in a Western European context. Two different methods suitable for hierarchically structured data sets were used for the meta‐analyses—hierarchical nonparametric bootstrapping and linear random effects models—, yielding nearly identical average outcomes but differing in terms of confidence intervals. We found that, on average, winter cover crops reduce cumulative seasonal (autumn‐winter) runoff by 68% and soil losses by 72% compared with a bare soil. The occurrence and intensity of stubble tillage on the control plot is a key explanatory variable for the mitigation effect of winter cover crops. In potato crops, tied ridging reduces cumulative seasonal (spring–summer) runoff by a mean of 70% and soil erosion by 92%. Conservation (non‐inversion) tillage techniques alleviate cumulative seasonal overland flow by 27% and associated sediments losses by 66%, but strong evidence of publication bias was detected for this farming practice, probably leading to an overestimation of its effectiveness. These mitigation effects are shown to be much greater for spring crops than for winter crops, and to increase with time since ploughing was stopped. The type of conservation tillage scheme strongly affects the ability to attenuate surface flows. Intensive non‐inversion tillage systems relying on repeated use of (powered) tillage operations appear to be the least effective for reducing both water and sediment losses. The best performing scheme against runoff would be a deep (non‐inversion) tillage (−61%), while against erosion it would be a no‐till system (−82%). Although several explanatory factors were identified, there remains a high (unexplained) variability between trials effect sizes, thus not attributable to pure sampling variability. Meanwhile, this review provides farm advisors or policy makers with guidance on the contexts in which implementation of such conservation practices should be supported so as to maximize expected benefits.

Reliability, stability during long-term storage, and intra-individual variation of circulating levels of osteopontin, osteoprotegerin, vascular endothelial growth factor-A, and interleukin-17A

BackgroundStudies in many populations have reported associations between circulating cytokine levels and various physiological or pathological conditions. However, the reliability of cytokine measurements in population studies, which measure cytokines in multiple assays over a prolonged period, has not been adequately examined; nor has stability during sample storage or intra-individual variation been assessed.MethodsWe assessed (1) analytical reliability in short- and long-term repeated measurements; (2) stability and analytical reliability during long-term sample storage, and (3) variability within individuals over seasons, of four cytokines—osteopontin (OPN), osteoprotegerin (OPG), vascular endothelial growth factor-A (VEGF-A), and interleukin-17A (IL-17A). Measurements in plasma or serum samples were made with commercial kits according to standard procedures. Estimation was performed by fitting a random or mixed effects linear model on the log scale.ResultsIn repeated assays over a short period, OPN, OPG, and VEGF-A had acceptable reliability, with intra- and inter-assay coefficients of variation (CV) less than 0.11. Reliability of IL-17A was poor, with inter- and intra-assay CV 0.85 and 0.43, respectively. During long-term storage, OPG significantly decayed (− 33% per year; 95% confidence interval [− 54, − 3.7]), but not OPN or VEGF-A (− 0.3% or − 6.3% per year, respectively). Intra- and inter-assay CV over a long period were comparable to that in a short period except for a slight increase in inter-assay CV of VEGF-A. Within-individual variation was small for OPN and VEGF-A, with intra-class correlations (ICC) 0.68 and 0.83, respectively, but large for OPG (ICC 0.11).ConclusionsWe conclude that OPN and VEGF-A can be reliably measured in a large population, that IL-17A is suitable only for small experiments, and that OPG should be assessed with caution due to degradation during storage and intra-individual variation. The overall results of our study illustrate the need for validation under relevant conditions when measuring circulating cytokines in population studies.

Baseline Frailty and Domain‐specific Cognitive Declines in Healthy and MCI Older Adults

AbstractBackgroundBoth physical frailty and cognitive decline increase with age and each place adults at elevated risk for loss of independence. Inconsistent associations have been found between frailty and risk for cognitive declines across cognitive domains. However, most studies were cross‐sectional and did not include a comprehensive battery of neuropsychological tests. We hypothesized that frail older adults, whether with or without Mild Cognitive Impairment (MCI) at baseline, are at risk for accelerated domain‐specific cognitive declines.MethodThe Ginkgo Evaluation of Memory Study (GEMS) was a prospective study of 3069 dementia‐free older adults aged 72‐96 years, followed for up to 7.5 years or a diagnosis of dementia, 482 of whom were diagnosed with MCI at baseline. A modified physical frailty phenotype was constructed using GEMS baseline data. A Neuropsychological Battery consisted of 13 tests reflecting global cognition, memory, visual‐spatial construction, language, psychomotor speed/attention, and executive function were administered annually. Linear random effects models were used to compare differences in baseline and rate of change in domain scores among individuals with and without baseline frailty.ResultOverall, frail participants showed poorer baseline cognitive function in all domains, and greater declines in all cognitive domains. When stratified by baseline MCI, among non‐MCI participants, those with frailty revealed poorer baseline psychomotor speed/attention and executive function, and greater declines in all cognitive domains. Among MCI participants, those with frailty exhibited lower baseline visual‐spatial construction, and greater declines in all cognitive domains except for visual‐spatial construction and executive function. In all cognitive domains, the estimated effect of frailty on cognitive decline was greater in MCI participants than non‐MCI participants.ConclusionFrailty was predictive of accelerated cognitive declines across domains and more so in those with baseline MCI. The results from this study highlight the importance of assessing frailty as a risk factor for accelerated cognitive declines, particularly among those at elevated preclinical cognitive risk. These individuals may be at the greatest risk of transitioning to dementia.

Adverse Childhood Experiences and Primary Headache Disorders: A Systematic Review, Meta-analysis, and Application of a Biological Theory.

Headache disorders are among the leading causes of disability worldwide. While an association between adverse childhood experiences and primary headaches has been reported, the pooled magnitude across studies and pathways of the association are unknown. Our objectives were (1) to estimate the pooled effect of ≥1 adverse childhood experience (ACE) on primary headache disorders in adulthood and (2) to test the hypothesis that ACEs categorized as "threat" traumas or "deprivation" traumas have distinct effects on primary headaches based on a selected theory from our narrative review of how ACEs affect human development along the life course. PubMed, EMBASE, MEDLINE, Web of Science, Google Scholar, Biological Psychiatry, and gray literature were searched up to March 16, 2023 (PROSPERO, CRD42020223403). Selected articles included (1) observational studies with a comparator group, (2) ACEs that occurred before 18 years of age, and (3) primary headaches occurring at or after 21 years of age. Pooled odds ratios (ORs) were calculated using multilevel linear random-effects modeling. The narrative review included theories that describe how ACEs affect human development and disease across the life course. We selected a theory from our narrative review and tested ACEs categorized according to this theory for any modification of point estimates. Our search identified 32 studies, of which 28 were eligible for meta-analysis (n = 154,739 participants, 19 countries). The occurrence of ≥1 adverse childhood experience(s) was associated with primary headaches (pooled OR = 1.48 [95% CI 1.36-1.61]; high-quality evidence, 134,696 participants). As the number of ACEs increased, the odds of primary headaches increased (range: 1 ACE OR = 1.24 [95% CI 1.14-1.35] to ≥4 ACEs OR = 2.09 [95% CI 1.83-2.38], p for trend <0.0001). From the narrative review, a neurodevelopmental theory that categorizes ACEs into threat or deprivation was tested, and both were independently associated with primary headaches (threat OR = 1.46 [95% CI 1.32-1.60] and deprivation OR = 1.35 [95% CI 1.23-1.49], respectively), accounting for heterogeneity (p = 0.021). This systematic review and meta-analysis confirm that ACEs are important risk factors of primary headache disorders in adulthood. Our findings provide epidemiologic support that ACEs categorized as threat and deprivation may manifest as distinct pathways of early adversity.

Efficacy of Willis covered stent of intracranial pseudoaneurysms in the internal carotid artery: A systematic review and meta-analysis

Objective: To evaluate the efficacy of a novel coated stent in the treatment of intracranial pseudoaneurysm. Methods: MEDLINE, EMBASE, and PubMed databases were searched for literature published between 1990 and April 2022 according to PRISMA guidelines. All studies with ≥10 patients reporting successful implantation of Willis covered stent, therapeutic effect, complications, and postoperative follow-up were included. The combined incidence and corresponding 95% confidence intervals were assessed using a generalized linear mixed method and random effects model. Results: Five studies (116 patients with pseudoaneurysms) were included. The experimental groups in the selected studies showed a combined technical success rate of 81.03% (OR=18.31, 95% CI=9.39-35.69, I 2=79%, P&lt;0.001). Clinical follow-up showed that the complete cure rate was as high as 94.4% after the follow-up (OR=106.81, 95% CI=39.08-291.88, I 2=0%, P=0.71). Conclusions: Willis covered stent is feasible, safe, and effective in the treatment of intracranial pseudoaneurysm.

Factors associated with mental health outcomes after COVID-19: A 24-month follow-up longitudinal study

ObjectiveInvestigate the proportion of mental health outcomes (MHOs) and associated factors in COVID-19 survivors during a 24-month follow-up period. MethodAn observational, prospective study was performed in a teaching hospital in Barranquilla, Colombia, from April 1, 2020, to August 30, 2022. A cohort of 1565 COVID-19 survivors was recruited after discharge from the emergency room (ER), inpatient floor (IF), and intensive care unit (ICU) services and followed for 24 -months. The clinical assessment included screening scales for symptoms of anxiety, depressive, post-traumatic stress disorder (PTSD), and insomnia. Sociodemographic and clinical factors were also collected to identify possible associated factors. Descriptive, bivariate and mixed random-effect linear models were performed. ResultsA total of 1565 patients were included, of whom 785 (50.35%) were men. A large proportion of patients with mental symptoms were identified. After 24-months, the proportions of anxiety, depression, PTSD, and insomnia symptoms remained high at 16.55%, 21.79%, 35.27%, and 23.86%, respectively. Social factors, location of hospital stays, physical comorbidities, and the severity of COVID-19 were significantly associated with anxiety, depression, PTSD, and insomnia symptoms. ConclusionsCOVID-19's 2-year deleterious impacts on mental health, as well as the variables influencing these findings, have been documented. These results should aid in the development of public health initiatives to reduce morbidity rates in post-COVID-19 patients.

A comparative study of different variable selection methods based on numerical simulation and empirical analysis.

This study employs the principles of computer science and statistics to evaluate the efficacy of the linear random effect model, utilizing Lasso variable selection techniques (including Lasso, Elastic-Net, Adaptive-Lasso, and SCAD) through numerical simulation and empirical research. The analysis focuses on the model's consistency in variable selection, prediction accuracy, stability, and efficiency. This study employs a novel approach to assess the consistency of variable selection across models. Specifically, the angle between the actual coefficient vector β and the estimated coefficient vector is computed to determine the degree of consistency. Additionally, the boxplot tool of statistical analysis is utilized to visually represent the distribution of model prediction accuracy data and variable selection consistency. The comparative stability of each model is assessed based on the frequency of outliers. This study conducts comparative experiments of numerical simulation to evaluate a proposed model evaluation method against commonly used analysis methods. The results demonstrate the effectiveness and correctness of the proposed method, highlighting its ability to conveniently analyze the stability and efficiency of each fitting model.

Modeling fuel consumption in various external vehicle conditions for military vehicle using mixed linear models

With the crisis in fuel consumption, it is necessary to save fuel consumption by selecting fuel that is quite efficient. The aim of the research is to examine the fuel consumption patterns of vehicles in an area that experiences various weathers so as to determine the level of efficiency of fuel use. both from the factor of fuel type, distance, speed, temperature, to the weather. testing was carried out using the linear model technique, the Linear Mixed effect model, and the Anova mathematical model. The results of the analysis if the different types of fuel have a very large significant effect in influencing the fuel consumption of a vehicle. With all the approaches analyzed from the linear mix model, analysis of variance and linear mix random effect model, the results show that other independent variables such as average speed, distance traveled and ambient temperature do not have much effect on fuel consumption. Based on modeling results that has been done, it can be identified if fuel consumption is strongly influenced by the type of fuel used by the vehicle. Meanwhile, other variables such as vehicle mileage, average speed, and ambient temperature at the time of data collection did not show any significant effect on fuel consumption.

Seasonal dynamics of herbaceous layer biomass and its contribution to annual net primary production in an oak–hornbeam forest

The role of the herbaceous layer in carbon assimilation and nutrient cycling is still undiscovered and unappreciated. One reason is that simple methods of annual net primary production (ANPP) estimation often underestimate its value, while more accurate methods are too labor-demanding. Moreover, studies on herbaceous layer and litterfall biomass in the same study site are extremely rare and usually conducted during one vegetation season, providing temporally-specific estimates. We hypothesized that (1) the seasonal herb layer biomass dynamics show a two-peak shape and (2) contribution of herbaceous layer biomass production in annual litter production was not more than 5% of tree litterfall. We studied the herb layer and litterfall biomass dynamics in an oak-hornbeam forest in W Poland for three years (January 2013 – October 2015). Samples of the herb layer (ten samples for four sample plots) were collected weekly in March, April and May or every two weeks for the remainder of each year, and litterfall was collected every month. All herb plants were cut at the soil level from circular frames with an area of 0.16 m2. Litterfall was studied with thirty litter traps (height of 15 cm, and catching area of 0.36 m2). We performed Kruskal–Wallis tests with Dunn’s post hoc tests to assess differences in variables among all collection times and linear random effects models to assess variance sources. We observed the highest biomass in 2013 on May 3rd (47.05 g m−2), and the lowest on October 30th in 2015 (4.69 g m−2). The seasonal herb layer biomass dynamic showed a single-peak shape; a very distinct peak occurred in spring and continued in late spring, summer, and early autumn. The spring ephemeralAnemone nemorosahad the highest share of herbaceous layer ANPP with 27% and was responsible for the spring biomass peak every season. The mean contribution of the herb layer biomass in annual litterfall was 9.23%. Our results highlight the underestimation of the herb layer role in biomass production in forest ecosystems in previous studies.

Efficient peer effects estimators with group effects

We study linear peer effect models where peers interact in groups and individual’s outcomes are linear in the group mean outcome and characteristics. We allow for unobserved random group effects as well as observed fixed group effects. The specification is in part motivated by the moment conditions imposed in Graham (2008). We show that these moment conditions can be cast in terms of a linear random group effects model and that they lead to a class of GMM estimators with parameters generally identified as long as there is sufficient variation in group size or group types. We also show that our class of GMM estimators contains a Quasi Maximum Likelihood estimator (QMLE) for the random group effects model, as well as the Wald estimator of Graham (2008) and the within estimator of Lee (2007) as special cases. Our identification results extend insights in Graham (2008) that show how assumptions about random group effects, variation in group size and certain forms of heteroscedasticity can be used to overcome the reflection problem in identifying peer effects. Our QMLE and GMM estimators accommodate additional covariates and are valid in situations with a large but finite number of different group sizes or types. Because our estimators are general moment based procedures, using instruments other than binary group indicators in estimation is straight forward. Our QMLE estimator accommodates group level covariates in the spirit of Mundlak and Chamberlain and offers an alternative to fixed effects specifications. This model feature significantly extends the applicability of Graham’s identification strategy to situations where group assignment may not be random but correlation of group level effects with peer effects can be controlled for with observable group level characteristics. Monte-Carlo simulations show that the bias of the QMLE estimator decreases with the number of groups and the variation in group size, and increases with group size. We also prove the consistency and asymptotic normality of the estimator under reasonable assumptions.

Severity and geographical disparities of post-COVID-19 symptoms among the Vietnamese general population: a national evaluation

Post-COVID-19 symptoms have become a significant global health concern. This study focused on assessing the prevalence, severity, and care preference of post-COVID-19 symptoms, as well as identifying determinants to inform evidence-based policy on post-COVID-19 in Vietnam. A national cross-sectional study was conducted in May 2022 among 12,361 recovered COVID-19 patients, providing the largest dataset on health status after COVID-19 in Vietnam. The study utilized ordered logistic, Poisson regression, Multilevel linear random-effects models, and Multilevel random effects ordered logistic model to identify factors associated with various aspects of post-COVID-19 conditions. Results showed that the average number of post-COVID-19 symptoms was approximately 3, with fatigue and headache being the most common symptoms. The number of post-COVID-19 symptoms varied by province, decreased with age, and was significantly correlated with the duration of infection. Age, infection period, underlying conditions, telehealth utilization, and geographical location were identified as significant determinants of post-COVID-19 symptoms. The study concluded that improving resource allocation and health-seeking behavior in underserved areas could help address differences in health outcomes and improve post-COVID-19 control in Vietnam.

The Associations of Birthweight for Gestational Age Status with Its Differential 0-2 Year Growth Trajectory and Blood Pressure at Two Years of Age in Chinese Boys and Girls.

The first 1000 days of life represents a critical period for lifelong metabolic health. This study prospectively examined the contrasts between the growth trajectories of large, small, and appropriate sizes for gestational age (LGA, SGA, and AGA) term-born infants in their first two years, and their blood pressure at two years. In 2012-2013, 806 Chinese mother-newborn dyads were enrolled in the Shanghai Obesity and Allergy Birth Cohort Study. Repeated anthropometric measures were obtained at age 42 days, and at 3, 6, 9, 12, 18 and 24 months. Systolic and diastolic blood pressure (SBP, DBP) were measured at two years of age. Linear random effect models were employed to evaluate growth trajectory differences between LGA, SGA, and AGA infants. Of the study infants, 12.4% were LGA and 4.0% SGA. Length, weight, and weight-for-length z-score (ZWFL) were all consistently higher in LGA infants and lower in SGA infants than AGA infants. SGA infants had a higher ZWFL (0.11 unit/month; 95% CI: 0.04, 0.19) and a higher BMI (0.19; 95% CI: 0.09, 0.28 kg/m2 per month) growth velocity at age 0-6 months, relative to AGA infants. SGA was associated with 6.4 (0.4-12.4) mmHg higher SBP, and LGA was associated with 2.9 (95% CI -5.2, -0.5) mmHg lower DBP at two years of age in boys, however, not in girls. In conclusion, in this prospective birth cohort with repeated anthropometric measures and BP at two years of age, LGA, SGA, and AGA term-born infants manifested differential patterns of weight growth trajectory and BP, providing new insight into developmental origins of cardiometabolic health.

Air pollution and plasma amyloid beta in a cohort of older adults: Evidence from the Ginkgo Evaluation of Memory study

Air pollution has been linked to Alzheimer’s disease and related dementias (ADRD), but the mechanisms connecting air pollution to ADRD have not been firmly established. Air pollution may cause oxidative stress and neuroinflammation and contribute to the deposition of amyloid beta (Aβ) in the brain. We examined the association between fine particulate matter<2.5 μm in diameter (PM2.5), particulate matter<10 μm in diameter (PM10), nitrogen dioxide (NO2), and plasma based measures of Aβ1-40, Aβ1-42 and Aβ1-42/Aβ1-40 using data from 3044 dementia-free participants of the Ginkgo Evaluation of Memory Study (GEMS). Air pollution exposures were estimated at residential addresses that incorporated address histories dating back to 1980, resulting in one-, five-, 10- and 20- year exposure averages. Aβ was measured at baseline (2000–2002) and then again at the end of the study (2007–2008) allowing for linear regression models to assess cross-sectional associations and linear random effects models to evaluate repeated measures. After adjustment for socio-demographic and behavioral covariates, we found small positive associations between each air pollutant and Aβ1-40 but no association with Aβ1-42 or the ratio measures in cross sectional analysis. In repeat measures analysis, we found larger positive associations between each air pollutant and all three outcomes. We observed a 4.43% (95% CI 3.26%, 5.60%) higher Aβ1-40 level, 9.73% (6.20%, 13.38%) higher Aβ1-42 and 1.57% (95% CI: 0.94%, 2.20%) higher Aβ1-42/Aβ1-40 ratio associated with a 2 µg/m3 higher 20-year average PM2.5. Associations with other air pollutants were similar. Our study contributes to the broader evidence base on air pollution and ADRD biomarkers by evaluating longer air pollution exposure averaging periods to better mimic disease progression and provides a modifiable target for ADRD prevention.