Baseline demographics and general characteristics of the participants in the initial cross-sectional (Canadian Obstructive Lung Disease (COLD)) cohort stratified into four smoking subgroups
| All participants | NS | T | M | MT | |
| Subjects | 5291 (100) | 2299 (43) | 1926 (36) | 181 (3) | 885 (17) |
| Age years | 59.0 (50.0–68.0) | 59.0 (50.0–68.0) | 65.0 (56.0–72.0)* | 51.0 (46.0–58.0)* | 53.0 (47.0–59.0)* |
| Male | 2443 (46.2) | 889 (38.7) | 897 (46.6)* | 114 (63.0)* | 543 (61.4)* |
| BMI kg·m−2 | 26.8 (24.0–30.5) | 26.5 (23.7–30.1) | 27.3 (24.4–31.2)* | 25.8 (23.3–29.4) | 26.9 (24.0–30.8)* |
| Education years of school | 15.0 (13.0–18.0) | 16.0 (14.0–18.0) | 14.0 (12.0–17.0)* | 17.0 (15.0–19.0)* | 15.0 (13.0–17.0)* |
| Marijuana smoking status | |||||
| Current | 346 (6.5) | 45 (24.9) | 301 (34.0) | ||
| Former | 720 (13.6) | 136 (75.1) | 584 (66.0) | ||
| Joint-years of marijuana | 1.6 (0.6–4.7) | 4.3 (1.3–12.9) | |||
| Years of smoking marijuana | 10.0 (4.0–20.0) | 12.0 (5.0–36.0) | |||
| Age of onset of marijuana smoking | 17.0 (15.0–20.0) | 18.0 (16.0–20.0) | 17.0 (15.0–19.0) | ||
| Tobacco smoking status | |||||
| Current | 726 (13.7) | 406 (21.1) | 320 (36.2) | ||
| Former | 2085 (39.4) | 1520 (78.9) | 565 (63.8) | ||
| Pack-years of tobacco | 18.8 (6.0–36.0) | 22.0 (10.0–36.3) | |||
| Years of smoking tobacco | 26.0 (14.0–39.0) | 27.0 (17.0–36.0) | |||
| Age of onset of tobacco smoking | 17.0 (15.0–20.0) | 16.0 (14.0–18.0) | |||
| Post-bronchodilator FEV1/FVC | 76.2 (70.8–80.7) | 77.4 (72.6–81.6) | 74.7 (67.8–79.6)* | 77.4 (73.9–81.5) | 75.9 (70.6–80.2)* |
| >20 joint-years# | 77.1 (72.9–80.7) | 74.0 (67.4–78.6)**** | |||
| ≤20 joint-years¶ | 77.5 (73.9–81.6) | 76.3 (71.3–80.6)**** | |||
| Post-bronchodilator FEV1 % pred | 95.4 (84.3–105.5) | 96.9 (86.8–106.2) | 93.2 (80.6–104.7)* | 99.0 (90.8–108.4)* | 95.0 (84.7–104.4)* |
| Post-bronchodilator FVC % pred | 96.5 (86.9–106.9) | 96.4 (87.2–106.0) | 95.6 (85.1–107.4) | 100.8 (92.1–110.9)* | 97.8 (89.5–107.1)* |
| COPD+ | 1204 (22.8) | 361 (15.7) | 612 (31.8))* | 19 (10.5) | 212 (24.0))* |
| Respiratory symptoms | |||||
| Chronic cough | 676 (12.8) | 215 (9.4) | 300 (15.6)* | 15 (8.3) | 146 (16.5)* |
| Chronic phlegm | 505 (9.5) | 145 (6.3) | 232 (12.1)* | 13 (7.2) | 115 (13.0)* |
| Wheezing | 1503 (28.4) | 494 (21.5) | 590 (30.6)* | 50 (27.6) | 369 (41.7)* |
| Dyspnoea mMRC score | 1.0 (1.0–2.0) | 1.0 (1.0–1.0) | 1.0 (1.0–2.0) | 1.0 (0.0–1.0) | 1.0 (1.0–2.0) |
Data are presented as n (%) or median (interquartile range). NS: never-smokers of either tobacco or marijuana; T: tobacco smoking only; M: marijuana smoking only; MT: smokers of both marijuana and tobacco; BMI: body mass index; joint-years: number of joints per day×total duration of smoking in years; pack-years: number of packs (20 cigarettes per pack) per day×total duration of smoking in years; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; COPD: chronic obstructive pulmonary disease; mMRC: modified Medical Research Council. #: n=17 (M), n=168 (MT); ¶: n=164 (M), n=717 (MT); +: the proportion of COPD in any marijuana smoker is 21.7%, and the proportion of COPD in any tobacco smoker is 29.3%. *: significantly different to NS as reference (p<0.05); ****: significantly different to each other (p<0.0001).