Systematic review of methods used in meta-analyses where a primary outcome is an adverse or unintended event

addresses: Peninsula College of Medicine and Dentistry, St Luke's Campus, University of Exeter, Exeter, UK. [email protected]: PMCID: PMC3528446types: Journal Article; Research Support, Non-U.S. Gov't© 2012 Warren et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Adverse consequences of medical interventions are a source of concern, but clinical trials may lack power to detect elevated rates of such events, while observational studies have inherent limitations. Meta-analysis allows the combination of individual studies, which can increase power and provide stronger evidence relating to adverse events. However, meta-analysis of adverse events has associated methodological challenges. The aim of this study was to systematically identify and review the methodology used in meta-analyses where a primary outcome is an adverse or unintended event, following a therapeutic intervention

Prenatal testosterone does not explain sex differences in spatial ability

The most consistent sex differences in cognition are found for spatial ability, in which males, on average, outperform females. Utilizing a twin design, two studies have shown that females with male co-twins perform better than females with female co-twins on a mental rotation task. According to the Twin Testosterone Transfer hypothesis (TTT) this advantage is due to in-uterine transmission of testosterone from males to females. The present study tested the TTT across 14 different spatial ability measures, including mental rotation tasks, in a large sample of 19–21-year-old twins. Males performed significantly better than females on all spatial tasks, with effect sizes ranging from η2 = 0.02 to η2 = 0.16. Females with a male co-twin outperformed females with a female co-twin in two of the tasks. The effect sizes for both differences were negligible (η2 < 0.02). Contrary to the previous studies, our results gave no indication that prenatally transferred testosterone, from a male to a female twin, influences sex differences in spatial ability

Prolonged rote learning produces delayed memory facilitation and metabolic changes in the hippocampus of the ageing human brain

Background: Repeated rehearsal is one method by which verbal material may be transferred from short- to long-term memory. We hypothesised that extended engagement of memory structures through prolonged rehearsal would result in enhanced efficacy of recall and also of brain structures implicated in new learning. Twenty-four normal participants aged 55-70 (mean = 60.1) engaged in six weeks of rote learning, during which they learned 500 words per week every week (prose, poetry etc.). An extensive battery of memory tests was administered on three occasions, each six weeks apart. In addition, proton magnetic resonance spectroscopy (H-1-MRS) was used to measure metabolite levels in seven voxels of interest (VOIs) (including hippocampus) before and after learning.Results: Results indicate a facilitation of new learning that was evident six weeks after rote learning ceased. This facilitation occurred for verbal/episodic material only, and was mirrored by a metabolic change in left posterior hippocampus, specifically an increase in NAA/(Cr+Cho) ratio.Conclusion: Results suggest that repeated activation of memory structures facilitates anamnesis and may promote neuronal plasticity in the ageing brain, and that compliance is a key factor in such facilitation as the effect was confined to those who engaged fully with the training