Table 3.
Incidence and the risk ratios of COPD exacerbation (≥ 1 moderate or ≥ 1 severe) during 1-year follow-up according to the presence of chronic bronchitis and BMI categories in 1264 patients from the KOCOSS
| Cases/at risk | Person-years | Incidence rate (per 1000 person-years) | Crude IRR (95% CI) | Adjusteda IRR (95% CI) | ||
|---|---|---|---|---|---|---|
| Model 1 | Model 2 | |||||
| Chronic bronchitis | ||||||
| Non-CB | 327/813 | 629 | 520 | Reference | Reference | Reference |
| CB | 224/451 | 317 | 707 | 1.36 (1.14–1.62) | 1.33 (1.12–1.59) | 1.19 (0.97–1.44) |
| BMI (kg/m2) | ||||||
| BMI ≥ 25 | 116/328 | 265 | 438 | Reference | Reference | Reference |
| BMI < 25 | 435/936 | 681 | 639 | 1.46 (1.19–1.79) | 1.20 (0.97–1.48) | 1.23 (0.97–1.56) |
| Chronic bronchitis and BMI (kg/m2) | ||||||
| Non-CB and BMI ≥ 25 | 76/230 | 189 | 402 | Reference | Reference | Reference |
| Non-CB and BMI < 25 | 251/583 | 439 | 572 | 1.43 (1.10–1.84) | 1.20 (0.89–1.55) | 1.21 (0.89–1.62) |
| CB and BMI ≥ 25 | 40/98 | 76 | 526 | 1.32 (0.90–1.94) | 1.36 (0.91–2.00) | 1.20 (0.77–1.88) |
| CB and BMI < 25 | 184/353 | 241 | 763 | 1.90 (1.45–2.49) | 1.58 (1.19–2.10) | 1.41 (1.02–1.91) |
P values < 0.05 are presented in bold. BMI, body mass index; CB, chronic bronchitis; CCI, Charlson comorbidity index; CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; ICS, inhaled corticosteroids; IRR, incidence rate ratios
aModel 1 was adjusted for age, sex, educational level, smoking status (current smoker vs. ex-smoker vs. never-smoker) and post bronchodilator FEV1(continuous). Model 2 was further adjusted for ICS use (yes vs. no), CCI (continuous) and exacerbation in the previous year (yes vs. no) in addition to Model 1