Meta-analysis of association studies on NAT2 slow acetylators and sporadic Parkinson's disease. The confidence interval for each study is given by a horizontal line, and the point estimate is given by a square whose height is inversely proportional to the standard error of the estimate. The summary odds ratio is drawn as a diamond with horizontal limits at the confidence limits and width inversely proportional to its standard error. (A): Meta-analysis on 10 studies. Test for heterogeneity χ2 (df 9) = 47.71 (p-value 0). The odds ratios are significantly different between the studies. The summary odds ratio (Mantel-Haenszel OR= 1.32, 95% CI, 1.12–1.54) is significantly greater than 1 (p < 0.05). (B) Meta-analysis on 8 studies, excluding studies of Bandmann et al. 2000 and Chan et al. 2003. The odds ratios are not significantly different between studies. Test for heterogeneity χ2 (df 7) = 14.28 (p = 0.0464). The summary odds ratio (OR= 1.07, 95% CI, 0.9–1.28) is not significant.