Table 1.
Description of analysis sample, stratified by cases and controls.
| Analysis sample (n = 544) | Cases; <LLN (n = 337) | Controls; ≥LLN (n = 207) | |
|---|---|---|---|
| Demographic and lifestyle information | |||
| Sex; n (%) male | 349/544 (64.2) | 230/337 (68.3) | 119/207 (57.5) |
| Age, mean (SD) | 69.6 (9.1) | 70.4 (7.9) | 68.2 (10.6) |
| Ethnicity; n (%) | |||
| White British | 517/537 (96.3) | 322/332 (97.0) | 195/205 (95.1) |
| Other | 20/537 (3.7) | 10/332 (3.0) | 10/205 (4.9) |
| Weight; n (%) | |||
| Underweight (BMI <18.5) | 9/514 (1.8) | 7/318 (2.2) | 2/196 (1.0) |
| Healthy (≥18.5 and <25) | 123/514 (23.9) | 85/318 (26.7) | 38/196 (19.4) |
| Overweight (≥25 and <30) | 194/514 (37.7) | 118/318 (37.1) | 76/196 (38.8) |
| Obese (≥30) | 188/514 (36.6) | 108/318 (34.0) | 80/196 (40.8) |
| BMI, mean (SD) n = 514 | 28.6 (5.4) | 28.1 (5.4) | 29.4 (5.4) |
| Smoking status; n (%) | |||
| Current smoker | 111/536 (20.7) | 79/332 (23.8) | 32/204 (15.7) |
| Ex-smoker | 361/536 (67.4) | 221/332 (66.6) | 140/204 (68.6) |
| Never smoker | 64/536 (11.9) | 32/332 (9.6) | 32/204 (15.7) |
| Employment status; n (%) | |||
| Employed | 88/534 (16.5) | 45/334 (13.5) | 43/200 (21.5) |
| Unemployed | 140/534 (26.2) | 94/334 (28.4) | 46/200 (23.0) |
| Retired | 306/534 (57.3) | 195/334 (58.4) | 111/200 (55.5) |
| Airflow obstruction | |||
| GOLD stage if <LLN | |||
| 1 (FEV1 ≥80% pred) | 87/337 (25.8) | 87/337 (25.8) | n/a |
| 2 (50–79%) | 177/337 (52.5) | 177/337 (52.5) | n/a |
| 3 (30–49%) | 59/325 (18.1) | 61/337 (18.1) | n/a |
| 4 (<30%) | 12/325 (3.6) | 12/337 (3.6) | n/a |
| Self-reported health and healthcare usage | |||
| MRC; n (%) | |||
| 1–2 | 219/427 (51.3) | 116/255 (45.5) | 103/172 (59.9) |
| 3–5 | 208/427 (48.7) | 139/255 (54.5) | 69/172 (40.1) |
| CAT impact level; n (%) | |||
| Low (0–9) | 180/406 (44.3) | 100/245 (40.8) | 80/161 (49.7) |
| Medium (10–20) | 146/406 (36.0) | 93/245 (38.0) | 53/161 (32.9) |
| High (21–30) | 69/406 (17.0) | 47/245 (19.2) | 22/161 (13.7) |
| Very high (31–40) | 11/406 (2.7) | 5/245 (2.0) | 6/161 (3.7) |
| Asthma; n (%) yes | 198/538 (36.8) | 129/334 (38.6) | 69/204 (33.8) |
| CVDa; n (%) yes | 159/538 (29.6) | 94/334 (28.1) | 65/204 (31.9) |
| Other comorbiditiesb; n (%) ≥1 | 302/540 (55.9) | 184/336 (54.8) | 111/204 (57.8) |
| Exacerbations in last 12 m; n (%) yes | 247/543 (45.5) | 182/336 (54.2) | 65/207 (31.4) |
| Respiratory hospitalisation in last 2 years; n (%) yes | 37/544 (6.8) | 27/337 (8.0) | 10/207 (4.8) |
LLN = below the 5th percentile of the predicted FEV1/FVC ratio using the NHANES III equations
aCVD was defined as self-reported coronary heart disease, heart failure or other heart condition
bOther comorbidities were defined as self-reported clinician diagnosis of diabetes, osteoporosis, depression, fracture