Use of hierarchical models for meta-analysis: experience in the metabolic ward studies of diet and blood cholesterol
✍ Scribed by Chris Frost; Robert Clarke; Heather Beacon
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 172 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0277-6715
No coin nor oath required. For personal study only.
✦ Synopsis
Overviews that combine single e!ect estimates from published studies generally use a summary statistic approach where the e!ect of interest is "rst estimated within each study and then averaged across studies in an appropriately weighted manner. Combining multiple regression coe$cients from publications is more problematic, particularly when there are di!erences in study design and inconsistent reporting of e!ect sizes and standard errors. This paper describes the use of a hierarchical model in such circumstances. Its use is illustrated in a meta-analysis of the metabolic ward studies that have investigated the e!ect of changes in intake of various dietary lipids on blood cholesterol. These studies all reported average blood cholesterol for groups of individuals who were studied on one or more diets. Thirty-one studies had randomized cross-over designs, 12 had matched parallel group designs, 12 had non-randomized Latin square designs and 16 had other uncontrolled designs. The hierarchical model allowed the di!erent types of comparison (within-group between-diet, between matched group) that were made in the various studies to each contribute to the overall estimates in an appropriately weighted manner by distinguishing between-study variation, withinstudy between-matched-group variation and within-group between-diet variation. The hierarchical models do not require consistent speci"cation of e!ect sizes and standard errors and hence have particular utility in combining results from published studies where the relationships between a dependent variable and two or more predictors have been investigated using heterogeneous methods of analysis.