Figure 1

Forest plot of ever smoking of any product and COPD-part 1. Table 5 presents the results of a main meta-analysis for COPD based on 129 relative risk (RR) and 95% confidence interval (CI) estimates for ever smoking of any product (or cigarettes if any product not available). The individual study estimates are shown numerically and graphically on a logarithmic scale in Figures 1 and 2. The weights (inverse-variance) are also shown numerically, expressed as a percentage of the overall weight. The studies are sorted in order of sex within study reference (REF). In the graphical representation individual RRs are indicated by a solid square, with the area of the square proportional to the weight. Arrows indicate where the CI extends outside the range allocated. Where the RR value falls outside the range, the size of the plotting symbol indicates the weight but the position is not true to the scale.