Meta-analysis of 55 studies examining the association between BMI and lung cancer risk in non-smokers.

e22551 Background: Lung cancer remains a leading cause of cancer-related mortality worldwide, with well-established risk factors such as smoking and environmental exposures. However, the relationship between body mass index (BMI) and lung cancer risk in non-smokers has garnered increasing attention due to its potential implications for cancer prevention and public health. While obesity and overweight are traditionally associated with increased risks for various cancers, evidence suggests a protective role in certain contexts, including lung cancer among non-smokers. To clarify this complex relationship, we conducted a comprehensive meta-analysis to assess the potential impact of overweight and obesity on lung cancer risk in non-smoking populations. Methods: We conducted a systematic search of PubMed, Google Scholar, and Web of Science to identify studies investigating the association between BMI, overweight (BMI 25–29.9), obesity (BMI ≥30), and lung cancer risk in non-smokers. Studies were included if they were randomized controlled trials or observational studies involving human participants and reported hazard ratios (HRs) with confidence intervals (CIs) for lung cancer risk stratified by BMI categories. Statistical analyses were conducted using a random-effects model on the web-based platform MetaAnalysisOnline ( https://metaanalysisonline.com ) to estimate pooled HRs. Heterogeneity was quantified using the I² statistic, and publication bias was assessed via funnel plots. Results were presented using forest plots, funnel plots, and Z-score plots to ensure a comprehensive visualization of the data. Results: Data from 55 studies were included in the qualitative synthesis. In 35 studies analyzing the connection between overweight and lung cancer, a significant risk reduction was observed (HR = 0.85, CI = 0.80–0.90, p < 0.01). Similarly, in 36 studies examining obesity, there was a significant reduction in lung cancer risk (HR = 0.83, CI = 0.77–0.89, p < 0.01). These findings were further substantiated by 15 case-control studies, which reported a pooled HR of 0.77 (CI = 0.63–0.94, p < 0.01). Although significant heterogeneity was noted across all analyses, no evidence of publication bias was detected. Conclusions: Our meta-analysis highlights a statistically significant reduction in lung cancer risk associated with both overweight and obesity in non-smokers. While the protective association observed may reflect confounding factors or reverse causality, it underscores the importance of stratifying lung cancer risk by smoking status and BMI in future studies.