Variables* | O3 exposure, ppb | ||
<58 | 58–77 | ≥78 | |
HAP | |||
No | 1.00 (Reference) | 1.52 (0.82–2.74) | 1.71 (0.98–3.02) |
Yes | 1.70 (1.03–2.89)† | 2.74 (1.78–4.45)§ | 3.94 (2.53–6.41)§ |
Smoking status | |||
Never | 1.00 (Reference) | 1.43 (1.04–1.98)† | 2.13 (1.55–2.94)§ |
Ever | 0.71 (0.33–1.37) | 1.52 (1.04–2.24)† | 1.79 (1.18–2.71)‡ |
History of TB | |||
No | 1.00 (Reference) | 1.53 (1.14–2.07)‡ | 2.15 (1.61–2.92)§ |
Yes | 0.89 (0.26–2.24) | 2.04 (1.07–3.66)† | 1.99 (1.01–3.67)† |
History of asthma | |||
No | 1.00 (Reference) | 1.57 (1.17–2.13)‡ | 2.20 (1.64–2.97)§ |
Yes | 1.70 (0.50–4.46) | 2.30 (1.10–4.43)† | 2.49 (1.10–5.09)† |
Occupational exposure | |||
No | 1.00 (Reference) | 1.64 (1.22–2.23)‡ | 2.18 (1.22–2.23)§ |
Yes | 1.85 (0.74–4.00) | 1.87 (1.22–2.84)‡ | 1.57 (0.84–2.76) |
*First, we adjusted the common variables to be age, sex, BMI and education. Then we set grouping factor as dummy variable in combination with risk factors of COPD with adjusting for other variables. For example, when HAP as group variable, we adjusted for history of asthma, history of TB and environmental exposures (smoking status and occupational exposure).
†P<0.05.
‡P<0.01.
§P<0.001.
BMI, body mass index; COPD, chronic obstructive pulmonary disease; HAP, household air pollution; O3, ozone; ppb, parts per billion; TB, tuberculosis.