Prolonged smoking duration is independently associated with mortality in former smokers with COPD regardless of...

Smoking exposure has been quantified using pack-years, which integrates smoking intensity and duration. However, pack-years may not fully capture the prognostic impact of prolonged exposure. We aimed to compare the prognostic value of smoking duration and cumulative smoking intensity for mortality risk stratification in patients with chronic obstructive pulmonary disease (COPD).

We analyzed data from the Korea COPD Subtype Study, an ongoing prospective multicenter cohort (NCT02800499). Smoking exposure was categorized using thresholds of 40 pack-years and 40 years of smoking duration. The primary outcome was all-cause mortality and the secondary outcome was cause-specific mortality.

Among 2166 patients with COPD, 210 deaths occurred over a median follow-up of 7 years. Smoking duration ≥40 years was associated with increased all-cause mortality risk regardless of cumulative smoking intensity. Compared with patients with <40 pack-years and smoking duration <40 years, those with <40 pack-years but smoking duration ≥40 years had higher all-cause mortality risk (adjusted hazard ratio [aHR] = 1.66; 95% confidence interval [CI] = 1.01-2.73). Similarly, patients with ≥40 pack-years and smoking duration ≥40 years had increased all-cause mortality risk (aHR = 1.58; 95% CI = 1.15-2.16). In contrast, ≥40 pack-years without prolonged smoking duration was not associated with all-cause mortality. In cause-specific mortality analyses, prolonged smoking duration was also associated with increased cardiovascular and cancer-related mortality.

Smoking duration was more strongly associated with mortality risk than cumulative smoking intensity alone and may provide additional prognostic information beyond pack-years for mortality risk stratification in patients with COPD.