Lung Cancer Risk Attributable to Active Smoking in China: A Systematic Review and Meta-Analysis.

Objective: No consensus exists on the relative risk ( RR) of lung cancer (LC) attributable to active smoking in China. This study aimed to evaluate the unified RR of LC attributable to active smoking among the Chinese population. Methods: A systematic literature search of seven databases was conducted to identify studies reporting active smoking among smokers versus nonsmokers in China. Primary articles on LC providing risk estimates with their 95% confidence intervals ( CIs) for "ever" "former" or "current" smokers from China were selected. Meta-analysis was used to estimate the pooled RR of active smoking. Results: Forty-four unique studies were included. Compared with that of nonsmokers, the pooled RR (95% CI) for "ever" "former" and "current" smokers were 3.26 (2.79-3.82), 2.95 (1.71-5.08), and 5.16 (2.58-10.34) among men, 3.18 (2.78-3.63), 2.70 (2.08-3.51), and 4.27 (3.61-5.06) among women, and 2.71 (2.12-3.46), 2.66 (2.45-2.88), and 4.21 (3.25-5.45) in both sexes combined, respectively. Conclusion: The RR of LC has remained relatively stable (range, 2-6) over the past four decades in China. Early quitting of smoking could reduce the RR to some extent; however, completely refraining from smoking is the best way to avoid its adverse effects.

The Association between Exposure to Second-Hand Smoke and Disease in the Chinese Population: A Systematic Review and Meta-Analysis.

Objective: To analyze the association between exposure to second-hand smoke (SHS) and 23 diseases, categorized into four classifications, among the Chinese population. Methods: We searched the literature up to June 30, 2021, and eligible studies were identified according to the PECOS format: Participants and Competitors (Chinese population), Exposure (SHS), Outcomes (Disease or Death), and Study design (Case-control or Cohort). Results: In total, 53 studies were selected. The odds ratio (OR) for all types of cancer was 1.79 (1.56-2.05), and for individual cancers was 1.92 (1.42-2.59) for lung cancer, 1.57 (1.40-1.76) for breast cancer, 1.52 (1.12-2.05) for bladder cancer, and 1.37 (1.08-1.73) for liver cancer. The OR for circulatory system diseases was 1.92 (1.29-2.85), with a value of 2.29 (1.26-4.159) for stroke. The OR of respiratory system diseases was 1.76 (1.13-2.74), with a value of 1.82 (1.07-3.11) for childhood asthma. The original ORs were also shown for other diseases. Subgroup analyses were performed for lung and breast cancer. The ORs varied according to time period and were significant during exposure in the household; For lung cancer, the OR was significant in women. Conclusion: The effect of SHS exposure in China was similar to that in Western countries, but its definition and characterization require further clarification. Studies on the association between SHS exposure and certain diseases with high incidence rates are insufficient.