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Kaplan–Meier survival curves for COPD patients in the quitting-smoking group (n=92; 40 deaths) and continuing-smoking group (n=112; 73 deaths).
Notes: Patients in the quitting-smoking group had lower survival than those in the continuing-smoking group. There was a significant difference between the two groups (log-rank test, 13.59; P=0.0002).
