IVhet Model Research Articles

Aerobic Exercise And Cancer-Related Fatigue In Adults

BACKGROUND: Using the traditional random-effects model, a recent meta-analysis of randomized controlled trials reported a statistically significant standardized mean difference (SMD) reduction in cancer-related fatigue (CRF) as a result of aerobic exercise (SMD, -0.22, 95% CI, -0.39 to -0.04, p = 0.01). However, a recently developed inverse heterogeneity (IVhet) model has been shown to be more valid than the traditional random-effects model. PURPOSE: The purpose of this study was to compare these previous meta-analytic results with those using the IVhet model. METHODS: Using data from a previous meta-analysis that included 36 SMD effect sizes (ES’s) representing 2,830 adults (1,426 exercise, 1,404 control), results were pooled using the IVhet model. In addition, absolute and relative differences between the IVhet and random-effects results for CRF were calculated as well as influence analysis with each SMD ES deleted from the IVhet model once. Non-overlapping 95% confidence intervals were considered statistically significant. RESULTS: A statistically non-significant reduction in CRF fatigue was found as a result of aerobic exercise using the IVhet model (SMD, -0.08, 95% CI, -0.31 to 0.14, p = 0.46). The IVhet model yielded a SMD ES that was 0.14 (63.6%) smaller than the random-effects model. With each study deleted from the IVhet model once, results remained statistically non-significant with SMD ES’s ranging from -0.11 (95% CI, -0.33 to 0.11) to -0.06 (95% CI, -0.28 to 0.16). CONCLUSIONS: The results of the current study suggest that there is currently insufficient evidence to support the use of aerobic exercise for reducing CRF in adults. Future studies should consider use of the IVhet versus traditional random-effects model when conducting aggregate data meta-analyses. Supported by NIH Grant U54GM104942

Community-deliverable exercise and anxiety in adults with arthritis and other rheumatic diseases: a protocol for a systematic review and meta-analysis of randomised controlled trials

IntroductionWhile anxiety is a major public health problem in adults with arthritis and other rheumatic diseases (AORD), the effects of exercise on anxiety in adults are not well established despite...

Aerobic Exercise and Cancer-Related Fatigue in Adults: A Reexamination Using the IVhet Model for Meta-analysis.

Although the results of a recent meta-analysis using the traditional random effects model yielded a statistically significant standardized mean difference (SMD) reduction in cancer-related fatigue (CRF) as a result of aerobic exercise, a recently developed inverse heterogeneity (IVhet) model has been shown to be more valid than the traditional random effects model. The purpose of this study was to compare these previous meta-analytic results using the IVhet model. Using data from a previous meta-analysis that included 36 SMD effect sizes (ES) representing 2,830 adults (1,426 exercise, 1,404 control), results were pooled using the IVhet model. Absolute and relative differences between the IVhet and random effects results for CRF were also calculated as well as influence analysis with each SMD ES deleted from the IVhet model. Nonoverlapping 95% confidence intervals (CI) were considered statistically significant. A statistically nonsignificant reduction in CRF fatigue was found as a result of aerobic exercise using the IVhet model (SMD, -0.08; 95% CI, -0.31-0.14; P = 0.46). The IVhet model yielded a SMD ES that was 0.14 (63.6%) smaller than the random effects model. With each study deleted from the IVhet model once, results remained statistically nonsignificant with SMD ESs ranging from -0.11 (95% CI, -0.33-0.11) to -0.06 (95% CI, -0.28-0.16). Insufficient evidence currently exists to support the use of aerobic exercise for reducing CRF in adults. Additional studies are needed to determine the certainty of aerobic exercise on CRF in adults. Cancer Epidemiol Biomarkers Prev; 26(2); 281-3. ©2016 AACR.

Advances in the meta-analysis of heterogeneous clinical trials I: The inverse variance heterogeneity model

This article examines an improved alternative to the random effects (RE) model for meta-analysis of heterogeneous studies. It is shown that the known issues of underestimation of the statistical error and spuriously overconfident estimates with the RE model can be resolved by the use of an estimator under the fixed effect model assumption with a quasi-likelihood based variance structure — the IVhet model. Extensive simulations confirm that this estimator retains a correct coverage probability and a lower observed variance than the RE model estimator, regardless of heterogeneity. When the proposed IVhet method is applied to the controversial meta-analysis of intravenous magnesium for the prevention of mortality after myocardial infarction, the pooled OR is 1.01 (95% CI 0.71–1.46) which not only favors the larger studies but also indicates more uncertainty around the point estimate. In comparison, under the RE model the pooled OR is 0.71 (95% CI 0.57–0.89) which, given the simulation results, reflects underestimation of the statistical error. Given the compelling evidence generated, we recommend that the IVhet model replace both the FE and RE models. To facilitate this, it has been implemented into free meta-analysis software called MetaXL which can be downloaded from www.epigear.com.