Table 1.
Meta-analysed characteristics of AO compared with asthma-only and COPD-only in population-based and clinic-based cohorts
| Population-based cohorts | Asthma-based cohorts | COPD-based cohorts | |||||
| AO | Asthma-only | COPD-only | AO | Asthma-only | AO | COPD-only | |
| Characteristics | |||||||
| Age (years), mean (95% CI) | 63.8 (59.4–68.3) | 62.5 (55.8–69.2) | 65.6 (60.1–71.0) | 61.7 (60.7–62.7) | 58.7 (55.9–61.5) | 65.6 (63.3–67.9) | 67.0 (64.7–69.4) |
| Female, prop (95% CI) | 53.3 (50.5–56.0) | 64.4 (59.1–69.7) | 46.9 (42.9–51.0) | 42.3 (34.1–50.6) | 60.6 (57.1–64.1) | 30.7 (6.1–55.3) | 22.3 (8.5–36.1) |
| BMI (kg/m2), mean (95% CI) | 26.7 (26.4–26.9) | 28.5 (27.8–29.2) | 26.2 (26.1–26.4) | 26.4 (24.5–28.4) | 28.3 (26.0–30.6) | 27.7 (26.1–29.3) | 27.3 (26.4–28.2) |
| Underweight, prop (95% CI) | 1.0 (0.5–1.5) | 0.2 (0.0–0.5) | 0.9 (0.2–1.6) | 1.6 (0.0–3.4) | 0.8 (0.0–2.6) | 3.7 (1.7–5.7) | 2.6 (1.0–4.3) |
| Normal weight, prop (95% CI) | 36.4 (32.3–40.4) | 23.4 (19.5–27.2) | 38.7 (35.7–41.6) | 40.4 (23.3–57.4) | 28.3 (21.9–34.7) | 28.4 (14.2–42.5) | 30.3 (22.6–37.9) |
| Overweight, prop (95% CI) | 42.9 (36.9–48.9) | 42.1 (39.2–45.1) | 45.0 (40.8–49.2) | 41.4 (34.3–48.5) | 40.1 (29.5–50.7) | 36.9 (33.6–40.1) | 38.2 (35.3–41.0) |
| Obese, prop (95% CI) | 18.5 (16.4–20.6) | 35.0 (27.6–42.3) | 15.4 (13.7–17.1) | 16.3 (0.0–32.8) | 31.1 (12.3–50.0) | 23.2 (20.1–26.3) | 27.9 (21.4–34.3) |
| Never smoker, prop (95% CI) | 29.7 (24.4–35.0) | 37.9 (34.4–41.5) | 22.3 (17.4–27.1) | 10.2 (5.2–15.1) | 26.2 (0.0–61.1) | 6.4 (0.0–15.2) | 1.7 (0.0–3.9) |
| Former smoker, prop (95% CI) | 52.8 (50.0–55.5) | 52.8 (46.7–59.0) | 49.2 (39.5–59.0) | 43.7 (17.0–70.3) | 34.2 (30.8–37.7) | 66.5 (63.3–69.6) | 61.2 (44.0–78.4) |
| Current smoker, prop (95% CI) | 17.4 (9.2–25.5) | 9.3 (6.4–12.1) | 28.4 (19.7–37.2) | 46.3 (14.7–77.9) | 39.7 (3.7–75.7) | 21.3 (5.1–37.5) | 37.1 (18.6–55.5) |
| Pack-years, mean (95% CI) | 21.2 (16.5–25.9) | 15.4 (11.2–19.5) | 25.3 (21.6–29.0) | 18.2 (11.4–25.0) | 17.5 (13.5–21.5) | 44.1 (34.5–53.8) | 57.2 (47.2–67.2) |
| mMRC score≥2, prop (95% CI) | 38.8 (21.9–55.7) | 24.4 (5.6–43.2) | 14.8 (0.4–29.2) | 54.7 (46.1–63.3) | 40.0 (35.7–44.2) | 51.3 (31.4–71.2) | 46.3 (32.4–60.2) |
| Allergic disease history, prop (95% CI) | 75.7 (73.0–78.5) | 74.9 (72.4–77.4) | 42.9 (41.7–44.0) | 70.3 (47.3–93.3) | 73.2 (61.9–84.4) | 44.1 (21.2–66.9) | 29.9 (24.0–35.8) |
| Chronic bronchitis, prop (95% CI) | 20.3 (10.9–29.8) | 14.4 (9.7–19.2) | 10.4 (5.6–15.2) | 31.7 (1.8–61.5) | 23.3 (0.0–46.9) | 57.2 (31.1–83.2) | 53.3 (34.9–71.7) |
| Emphysema, prop (95% CI) | – | – | – | – | – | 47.8 (4.4–91.1) | 46.5 (4.5–88.6) |
| Spirometry | |||||||
| FEV1 (%) predicted, mean (95% CI) | 75.0 (69.7–80.3) | 95.1 (92.5–97.8) | 81.8 (76.0–87.7) | 54.9 (41.1–68.6) | 80.4 (66.5–94.4) | 51.7 (45.2–58.1) | 51.1 (46.5–55.7) |
| FVC (%) predicted, mean (95% CI) | 93.0 (85.5–100.5) | 95.9 (92.1–99.7) | 97.8 (90.4–105.1) | 78.9 (76.2–81.6) | 88.8 (82.8–94.7) | 77.2 (72.9–81.5) | 77.1 (74.3–79.9) |
| FEV1/FVC (%), mean (95% CI) | 61.6 (59.7–63.6) | 77.0 (76.4–77.6) | 63.9 (63.4–64.5) | 54.2 (41.2–67.2) | 72.8 (57.7–87.8) | 51.6 (46.3–56.9) | 50.2 (46.3–54.1) |
| Biomarkers | |||||||
| Peripheral blood WBC (109 cells/L), mean (95% CI) |
6.7 (5.7–7.8) | 6.6 (5.5–7.7) | 6.9 (5.4–8.4) | 8.8 (7.8–9.7) | 7.6 (7.2–8.0) | 7.9 (7.7–8.1) | 7.7 (7.2–8.2) |
| BEC above 300 cells/µL, prop (95% CI) | 28.3 (25.3–31.2) | 18.0 (15.7–20.2) | 15.7 (14.8–16.5) | 47.0 (34.9–59.0) | 35.9 (29.4–42.4) | 24.0 (20.1–27.9) | 18.6 (11.1–26.0) |
| Serum CRP (mg/dL), median (IQR)* | – | – | – | 2.2 (3.5) | 2.1 (3.8) | 3.0 (3.8) | 3.7 (5.0) |
| Serum IgE (ie,/mL), median (IQR)* | – | – | – | 120 (292) | 110 (221) | 78 (192) | 54 (116) |
*Summary statistics of individual cohorts were meta-analysed, except for CRP and IgE for which only single-study data were available.
AO, asthma with airflow obstruction; BEC, blood eosinophil counts; COPD, chronic obstructive pulmonary disease; CRP, C reactive protein; FEV1, forced expiratory volume in 1 second; FEV1/FVC, ratio of FEV1 to FVC; FVC, forced vital capacity; IgE, immunoglobulin E; mMRC, modified Medical Research Council Dyspnoea; WBC, white blood cell count.