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Vegetarian Dietary Patterns and Cardiometabolic Risk in People With or at High Risk of Cardiovascular Disease: A Systematic Review and Meta-analysis.
Wang, T, Kroeger, CM, Cassidy, S, Mitra, S, Ribeiro, RV, Jose, S, Masedunskas, A, Senior, AM, Fontana, L
JAMA network open. 2023;(7):e2325658
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Abstract
IMPORTANCE Plant-based diets are known to improve cardiometabolic risk in the general population, but their effects on people at high risk of cardiovascular diseases (CVDs) remain inconclusive. OBJECTIVE To assess the association of vegetarian diets with major cardiometabolic risk factors, including low-density lipoprotein cholesterol (LDL-C), hemoglobin A1c (HbA1c), systolic blood pressure (SBP), and body weight in people with or at high risk of CVDs. DATA SOURCES This meta-analysis was registered before the study was conducted. Systematic searches performed included Embase, MEDLINE, CINAHL, and CENTRAL from inception until July 31, 2021. STUDY SELECTION Eligible randomized clinical trials (RCTs) that delivered vegetarian diets in adults with or at high risk of CVDs and measured LDL-C, HbA1c or SBP were included. Of the 7871 records screened, 29 (0.4%; 20 studies) met inclusion criteria. DATA EXTRACTION AND SYNTHESIS Two reviewers independently extracted data including demographics, study design, sample size, and diet description, and performed risk of bias assessment. A random-effects model was used to assess mean changes in LDL-C, HbA1c, SBP, and body weight. The overall certainty of evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool. MAIN OUTCOMES AND MEASURES Mean differences between groups in changes (preintervention vs postintervention) of LDL-C, HbA1c, and SBP; secondary outcomes were changes in body weight and energy intake. RESULTS Twenty RCTs involving 1878 participants (range of mean age, 28-64 years) were included, and mean duration of intervention was 25.4 weeks (range, 2 to 24 months). Four studies targeted people with CVDs, 7 focused on diabetes, and 9 included people with at least 2 CVD risk factors. Overall, relative to all comparison diets, meta-analyses showed that consuming vegetarian diets for an average of 6 months was associated with decreased LDL-C, HbA1c, and body weight by 6.6 mg/dL (95% CI, -10.1 to -3.1), 0.24% (95% CI, -0.40 to -0.07), and 3.4 kg (95% CI, -4.9 to -2.0), respectively, but the association with SBP was not significant (-0.1 mm Hg; 95% CI, -2.8 to 2.6). The GRADE assessment showed a moderate level of evidence for LDL-C and HbA1c reduction. CONCLUSIONS AND RELEVANCE In this study, consuming a vegetarian diet was associated with significant improvements in LDL-C, HbA1c and body weight beyond standard therapy in individuals at high risk of CVDs. Additional high-quality trials are warranted to further elucidate the effects of healthy plant-based diets in people with CVDs.
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The conundrum of human immune system "senescence".
Pawelec, G, Bronikowski, A, Cunnane, SC, Ferrucci, L, Franceschi, C, Fülöp, T, Gaudreau, P, Gladyshev, VN, Gonos, ES, Gorbunova, V, et al
Mechanisms of ageing and development. 2020;:111357
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Abstract
There is a great deal of debate on the question of whether or not we know what ageing is (Ref. Cohen et al., 2020). Here, we consider what we believe to be the especially confused and confusing case of the ageing of the human immune system, commonly referred to as "immunosenescence". But what exactly is meant by this term? It has been used loosely in the literature, resulting in a certain degree of confusion as to its definition and implications. Here, we argue that only those differences in immune parameters between younger and older adults that are associated in some definitive manner with detrimental health outcomes and/or impaired survival prospects should be classed as indicators of immunosenescence in the strictest sense of the word, and that in humans we know remarkably little about their identity. Such biomarkers of immunosenescence may nonetheless indicate beneficial effects in other contexts, consistent with the notion of antagonistic pleiotropy. Identifying what could be true immunosenescence in this respect requires examining: (1) what appears to correlate with age, though generality across human populations is not yet confirmed; (2) what clearly is part of a suite of canonical changes in the immune system that happen with age; (3) which subset of those changes accelerates rather than slows aging; and (4) all changes, potentially population-specific, that accelerate agig. This remains an immense challenge. These questions acquire an added urgency in the current SARS-CoV-2 pandemic, given the clearly greater susceptibility of older adults to COVID-19.
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Meta-Analysis of Copper and Iron in Parkinson's Disease Brain and Biofluids.
Genoud, S, Senior, AM, Hare, DJ, Double, KL
Movement disorders : official journal of the Movement Disorder Society. 2020;(4):662-671
Abstract
BACKGROUND Variations in study quality and design complicate interpretation of the clinical significance of consistently reported changes in copper and iron levels in human Parkinson's disease brain and biofluids. METHODS We systematically searched literature databases for quantitative reports of biometal levels in the degenerating substantia nigra (SN), CSF, serum, and plasma in Parkinson's disease compared with healthy age-matched controls and assessed the quality of these publications. The primary outcomes of our analysis confirmed SN copper and iron levels are decreased and increased, respectively, in the Parkinson's disease brain. We applied a novel Quality Assessment Scale for Human Tissue to categorize the quality of individual studies and investigated the effects of study quality on our outcomes. We undertook a random-effects meta-analysis and meta-regression subgroup analysis. RESULTS In the 18 eligible studies identified (211 Parkinson's disease, 215 control cases), SN copper levels were significantly lower (d, -2.00; 95% CI, -2.81 to -1.19; P < 0.001), and iron levels were significantly higher (d, 1.31; 95% CI, 0.38-2.24; P < 0.01) in Parkinson's disease. No changes were detected in CSF, serum, or plasma for any metals (29 studies; 2443 Parkinson's disease and 2183 control cases) except serum iron, which was lower in Parkinson's disease (14 studies; 1177 Parkinson's disease and 1447 control cases). CONCLUSIONS Reductions in copper levels and elevations in iron were confirmed as characteristic of the degenerating SN of Parkinson's disease. Iron in serum was also changed, but in the opposite direction to that in the SN and to a lesser extent. © 2019 International Parkinson and Movement Disorder Society.
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Revisiting and expanding the meta-analysis of variation: The log coefficient of variation ratio.
Senior, AM, Viechtbauer, W, Nakagawa, S
Research synthesis methods. 2020;(4):553-567
Abstract
Meta-analyses are often used to estimate the relative average values of a quantitative outcome in two groups (eg, control and experimental groups). However, they may also examine the relative variability (variance) of those groups. For such comparisons, two relatively new effect size statistics, the log-transformed "variability ratio" (the ratio of two standard deviations; lnVR) and the log-transformed "coefficients of variation ratio" (the ratio of two coefficients of variation; lnCVR) are useful. In practice, lnCVR may be of most use because a treatment may affect the mean and the variance simultaneously. We propose new estimators for lnCVR and lnVR, including for when the two groups are dependent (eg, cross-over and pre-test-post-test designs). Through simulation, we evaluated the bias of these estimators and make recommendations accordingly. We use the methods to demonstrate that: (a) lifestyle interventions have a heterogenizing effect on gestational weight gain in obese women and (b) low-glycemic index (GI) diets have a homogenizing effect on glycemic control in diabetics. We also find that the degree to which dependence among samples is accounted for can impact parameters such as τ2 (ie, the between-study variance) and I2 (ie, the proportion of the total variability due to between-study variance), and even the overall effect, and associated qualitative interpretations. Meta-analytic comparison of the variability between two groups enables us to ask completely new questions and to gain fresh insights from existing datasets. We encourage researchers to take advantage of these convenient new effect size measures for the meta-analysis of variation.