Active and passive smoking and the risk of breast cancer: An umbrella review of systematic reviews and meta-analyses

Both former and current smoking, as well as passive exposure to smoke, were associated with an elevated risk of breast cancer. The association with former smoking may reflect long-lasting biological damage, while current and passive smoking likely act through similar carcinogenic pathways. Further studies are needed to establish causality and to account for potential confounding factors such as genetic predisposition and lifestyle. These findings highlight the importance of smoking cessation programs and stricter regulations on secondhand smoke to mitigate the global burden of breast cancer.