| ECRHS | EGEA | NSHD | SALIA | SAPALDIA | |
| Total n | 3859 | 568 | 844 | 580 | 1764 |
| First spirometry | 1991–1993 | 1991–1995 | 1999 | 1985–1994 | 1991–1992 |
| Second spirometry | 2001–2002 | 2003–2007 | 2006–2010 | 2007–2009 | 2002 |
| Female | 1981 (51.3) | 303 (53.3) | 471 (55.8) | 580 (100.0) | 980 (55.6) |
| Age years | 43.0±7.2 | 53.1±11.3 | 63.3±1.1 | 73.3±3.4 | 53.2±11.0 |
| BMI kg·m−2 | 25.7±4.6 | 25.3±4.3 | 27.7±4.9 | 27.4±4.5 | 25.4±4.3 |
| Height cm | 168.6±9.5 | 168.5±8.4 | 167.4±8.6 | 162.3±5.5 | 168.8±9.0 |
| Ex-smoker | 1064 (27.6) | 206 (36.3) | 497 (58.9) | 99 (17.1) | 568 (32.2) |
| Current smoker | 1224 (31.7) | 81 (14.3) | 77 (9.1) | 18 (3.1) | 492 (27.9) |
| Pack years at first spirometry# | 7.7±12.0 | 5.9±10.0 | 9.1±12.6 | 2.8±8.4 | 10.9±17.9 |
| Pack years from first to second spirometry# | 3.9±10.9 | 1.7±8.3 | 0.7±2.5 | 0.6±6.7 | 3.1±6.5 |
| Medium educational level# | 1321 (34.2) | 118 (20.8) | 439 (52.0) | 276 (47.6) | 1121 (63.5) |
| High educational level# | 1420 (36.8) | 263 (46.3) | 102 (12.1) | 199 (34.3) | 520 (29.5) |
| Environmental tobacco exposure at home or at work# | 676 (17.5) | 233 (41.0) | 168 (19.9) | 347 (59.8) | 119 (6.7) |
| Occupational exposure to dust/fumes or gases# | 1685 (43.7) | 125 (22.0) | 246 (29.1) | 39 (6.7) | 460 (26.1) |
| Ever asthma#,¶ | 616 (16.0) | 183 (32.2) | 83 (9.8) | 50 (8.6) | 155 (8.8) |
| FEV1 L | 3.47±0.81 | 3.03±0.85 | 2.83±0.66 | 2.20±0.42 | 3.10±0.82 |
| FVC L | 4.33±1.00 | 4.00±1.01 | 3.57±0.81 | 2.91±0.54 | 4.08±1.02 |
| FEV1 change+ L | −0.026±0.032 | −0.028±0.031 | −0.022±0.025 | −0.020±0.014 | −0.033±0.030 |
| FVC change+ L | −0.018±0.040 | −0.015±0.037 | −0.025±0.034 | −0.022±0.019 | −0.022±0.041 |
Data are presented as mean±sd for continuous variables, or n (%) for categorical variables, unless otherwise stated. Characteristics refer to time point of second spirometry, and are presented for the larger subgroup of participants included in the analysis of NO2 and NOx and traffic indicators (characteristics for the smaller subgroup of participants included in the particulate matter metrics analyses are presented in supplementary table S1). BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity. #: information missing on a limited number of subjects; ¶: asthma diagnosed by a physician at first and/or at second spirometry; +: change in lung function between first and second spirometry.