The evidence is based on large studies from all around the world. However, the duration, reporting, and measuring of exposure varies across studies, and there was moderate heterogeneity (I2=52%) even after adjusting. Severe heterogeneity was found in sub-group analysis. Moreover, publication bias may be present.
| Reference | Study type | Population | Intervention and comparison | Outcomes | Risk of bias «Additional comments for included studies...»2 |
|---|---|---|---|---|---|
| SR=systematic review | |||||
| «Chen P, Li Y, Wu D, ym. Secondhand Smoke Exposure ...»1 | SR | 25,592 adult patients around the world from 1987 to 2021. Second-hand smoke exposure: 1) Someone at home or around the workplace smokes; 2) were exposed to tobacco smoke for several hours in a week. | People who had exposed vs. not exposed | COPD diagnosed according to GOLD 2022 criteria | moderate |
| Reference | Comments |
|---|---|
| «Chen P, Li Y, Wu D, ym. Secondhand Smoke Exposure ...»1 | Inclusion criteria for studies: Original cross-sectional, case-control, and cohort studies conducted, assessing the association between SHS exposure and COPD prevalence and determination of COPD followed the criteria in the 2022 Gold Report (The spirometric criterion for airflow limitation remains a post-bronchodilator fixed ratio of FEV1 (Forced Expiratory Volume in the first second) /FVC (Forced Vital Capacity) < 0.70), and the studies must include only non-smokers and ex-smokers in the population, or less than 50% of current smokers. Of these, 4 studies did not provide a specific description of SHS exposure, 7 studies described the duration of exposure, and 4 studies mentioned the number of packs or sticks of secondhand smoke inhaled per year. The duration of exposure to SHS varied greatly among different studies. |
Results
| Reference | Number of studies and number of patients (I/C) | Follow-up time | Absolute number of events (%) I | Absolute number of events (%) C | Odds Ratio (95% CI) |
|---|---|---|---|---|---|
| I= intervention; C=comparison; CI=confidence interval | |||||
| «Chen P, Li Y, Wu D, ym. Secondhand Smoke Exposure ...»1 | 13 RCTs (10060/7962) | from 1 to 41 years | 1415 (14) | 879 (11) | 1.52 (1.27;1.81) |
| Level of evidence: moderate The quality of evidence is downgraded due to imprecision and publication bias |
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