The primary objective of this study is to compare the efficacy of Tiotropium and placebo on improving HRQoL evaluated by the percentage of SGRQ responders. The null hypothesis is that there is no difference in the effect on HRQoL assessed by the percentage of SGRQ responders between the two treatment groups. The alternative hypothesis is that there is a difference in effect on HRQoL assessed by the percentage of SGRQ responders between tiotropium and placebo. The test will be performed at the alpha = 0.05 level of significance.