"The pooled odds ratio is 0.94 with 95 per cent confidence interval [0.69; 1.29] (p-value 0.7109). This (non-significant) effect reversion, produced by pooling, was observed by another author who in the light of these found the results of the meta-analysis 'intriguing' . It can be seen as a milder form of Simpson's paradox. "
[Show abstract][Hide abstract] ABSTRACT: Simpson's paradox is sometimes referred to in the areas of epidemiology and clinical research. It can also be found in meta-analysis of randomized clinical trials. However, though readers are able to recalculate examples from hypothetical as well as real data, they may have problems to easily figure where it emerges from.
First, two kinds of plots are proposed to illustrate the phenomenon graphically, a scatter plot and a line graph. Subsequently, these can be overlaid, resulting in a overlay plot. The plots are applied to the recent large meta-analysis of adverse effects of rosiglitazone on myocardial infarction and to an example from the literature. A large set of meta-analyses is screened for further examples.
As noted earlier by others, occurrence of Simpson's paradox in the meta-analytic setting, if present, is associated with imbalance of treatment arm size. This is well illustrated by the proposed plots. The rosiglitazone meta-analysis shows an effect reversion if all trials are pooled. In a sample of 157 meta-analyses, nine showed an effect reversion after pooling, though non-significant in all cases.
The plots give insight on how the imbalance of trial arm size works as a confounder, thus producing Simpson's paradox. Readers can see why meta-analytic methods must be used and what is wrong with simple pooling.
BMC Medical Research Methodology 02/2008; 8(1):34. DOI:10.1186/1471-2288-8-34 · 2.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is unknown why heart failure progresses even when patients are treated with the best therapy available. Evidences suggest that heart failure progression is due to loss of neurohumoral blockade in advanced stages of the disease and to alterations in myocardial metabolism induced, in part, by this neurohumoral activation. Alterations in cardiac energy metabolism, especially those related to substrate utilization and insulin resistance, reduce the efficiency of energy production, causing a heart energy reserve deficit. These events play a basic role in heart failure progression. Therefore, modulation of cardiac metabolism has arisen as a promissory therapy in the treatment of heart failure. This review describes myocardial energy metabolism, evaluates the role of impaired energy metabolism in heart failure progression and describes new therapies for heart failure involving metabolic intervention.
Revista medica de Chile 01/2010; DOI:10.4067/S0034-98872010000800014 · 0.30 Impact Factor
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