Method of staging (cut-off values) | Crude OR for ≥2 SAE at 1 year (95% CI) | Adjusted OR# for ≥2 SAE at 1 year (95% CI) | Crude OR for ≥1 SAE every year at 2 years (95% CI) | Adjusted OR# for ≥1 SAE every year at 2 years (95% CI) |
FEV1 % pred (GOLD) | ||||
1 (≥80%) | 1 | 1 | 1 | 1 |
2 (≥50% and <80%) | 0.25 (0.02–4.16) | 0.23 (0.01–5.49) | 0.98 (0.11–9.05) | 1.33 (0.11–15.51) |
3 (≥30% and <50%) | 7.12 (0.91–55.41) | 4.39 (0.34–56.46) | 5.85 (0.74–46.07) | 7.65 (0.75–78.06) |
4 (<30%) | 3.40 (0.29–39.92) | 1.61 (0.08–31.61) | 3.33 (0.28–39.43) | 5.21 (0.33–81.84) |
FEV1 % pred (quartiles) | ||||
1 (≥69.3%) | 1 | 1 | 1 | 1 |
2 (≥53.6% and <69.3%) | 1.00 (0.06–16.29) | 0.70 (0.04–13.86) | 2.06 (0.18–23.27) | 2.28 (0.19–27.98) |
3 (≥41.0% and <53.6%) | 10.11 (1.25–81.95)+ | 6.63 (0.66–67.11) | 12.90 (1.62–102.91)+ | 12.92 (1.49–112.32)+ |
4 (<41.0%) | 12.75 (1.60–101.48)+ | 6.82 (0.64–72.22) | 10.03 (1.24–81.50)+ | 11.68 (1.28–106.87)+ |
z-score (quartiles) | ||||
1 (≥−1.70) | 1 | 1 | 1 | 1 |
2 (≥−2.57 and < −1.70) | NA | NA | NA | NA |
3 (≥−3.17 and < −2.57) | 15.52 (1.97–121.95)+ | 12.34 (1.11–137.60)+ | 17.96 (2.29–140.97)+ | 25.62 (2.44–268.57)+ |
4 (<−3.17) | 9.25 (1.13–75.96)+ | 6.45 (0.51–81.31) | 8.77 (1.07–72.17)+ | 16.76 (1.47–190.99)+ |
(FEV1·Ht−2)A (quartiles) | ||||
1 (≥0.63) | 1 | 1 | 1 | 1 |
2 (≥0.47 and <0.63) | 1.87 (0.17–21.10) | 1.69 (0.12–24.38) | 1.78 (0.32–10.05) | 1.79 (0.28–11.31) |
3 (≥0.36 and <0.47) | 8.84 (1.08–72.51)+ | 5.89 (0.57–61.31) | 3.50 (0.70–17.49) | 3.17 (0.56–17.91) |
4 (<0.36) | 15.07 (1.89–120.29)+ | 8.46 (0.80–89.21) | 6.50 (1.36–31.00)+ | 6.22 (1.13–34.34)+ |
(FEV1·Ht−2)B¶ | ||||
1 (≥0.50) | 1 | 1 | 1 | 1 |
2 (≥0.40 and <0.50) | 3.02 (0.49–18.56) | 2.16 (0.32–14.87) | 1.45 (0.31–6.69) | 1.38 (0.29–6.70) |
3 (≥0.30 and <0.40) | 12.04 (2.59–56.08)§ | 8.54 (1.60–45.66)+ | 5.37 (1.61–17.90)+ | 5.35 (1.49–19.23)+ |
4 (<0.30) | 14.65 (2.80–76.68)§ | 8.41 (1.29–54.94)+ | 7.57 (1.98–28.95)§ | 8.33 (1.88–36.94)+ |
FEV1·Ht−3 (quartiles) | ||||
1 (≥0.38) | 1 | 1 | 1 | 1 |
2 (≥0.29 and <0.38) | 3.29 (0.34–32.36) | 3.01 (0.25–37.03) | 2.09 (0.37–11.79) | 2.17 (0.35–13.40) |
3 (≥0.22 and <0.29) | 7.79 (0.94–64.87) | 5.90 (0.57–60.91) | 4.18 (0.86–20.40) | 4.01 (0.74–21.69) |
4 (<0.22) | 16.71 (2.09–133.34)+ | 9.88 (0.97–100.50) | 6.43 (1.33–31.06)+ | 6.29 (1.15–34.42)+ |
FEV1Q (quartiles) | ||||
1 (≥3.38) | 1 | 1 | 1 | 1 |
2 (≥2.50 and <3.38) | 2.00 (0.18–22.54) | 2.12 (0.14–31.40) | 1.46 (0.24–8.99) | 1.51 (0.22–10.61) |
3 (≥1.90 and <2.50) | 8.85 (1.08–72.65)+ | 6.41 (0.57–72.18) | 3.67 (0.73–18.32) | 3.54 (0.61–20.62) |
4 (<1.90) | 12.95 (1.63–103.15)+ | 7.83 (0.70–87.15) | 6.48 (1.38–30.48)+ | 7.11 (1.26–40.01)+ |
FEV1: forced expiratory volume in 1 s; FEV1 % pred: percentage of predicted FEV1; GOLD: Global Initiative for Chronic Obstructive Lung Disease; FEV1·Ht−2: FEV1 over height squared; FEV1·Ht−3: FEV1 over height cubed; FEV1Q: FEV1 quotient; NA: statistical estimate could not be obtained owing to too few event counts. #: adjustment was made for age, body mass index, Charlson comorbidity index, smoking status, and history of SAE in the preceding year; ¶: the cut-off values (0.3, 0.4, 0.5) were proposed in [7]; +: p<0.05; §: p<0.005.