Secondhand smoke (SHS) continues to be a major global health risk, contributing to cardiovascular diseases, metabolic disorders, and respiratory illnesses. Using data from the Global Burden of Disease 2021 study across 204 countries, this analysis examined the burden of SHS exposure through Disability-Adjusted Life Years (DALYs) across different socio-demographic regions. The findings show notable sex and regional disparities: ischemic heart disease caused a higher burden among males, while diabetes and stroke affected females more. COPD had the highest burden in lower-middle SDI regions...