Passive Smoking, Coronary Heart Disease, and Meta-Analysis

Meta-analysis — the formal combination of the research results from multiple studies — is widely used, but with little general understanding of its limitations and uncertainties. There is something quite appealing about collecting all the available research on some question and reducing it to a single figure or a single confidence interval. When properly used, this approach can be useful. However, there is broad evidence that the results of meta-analyses are often not very reliable. LeLorier et al.1 have shown that many meta-analyses do not agree with the results of subsequent large, randomized trials, and there is little reason to . . .