Second-hand smoke has been linked to a major global burden of heart disease, with ischaemic heart disease emerging as the leading cause of deaths attributable to tobacco smoke exposure, a new study published in The Lancet Public Health has found.
The study estimates that 2.71 billion people worldwide were exposed to second-hand smoke (SHS) in 2023, with the exposure associated with 1.66 million deaths and 44.8 million disability-adjusted life years (DALYs).
Of the deaths attributed to SHS, ischaemic heart disease accounted for the largest share, with an estimated 537,000 deaths globally in 2023. Chronic obstructive pulmonary disease followed with 354,000 deaths, stroke with 278, lower respiratory diseases with 185,000, and tracheal, bronchus and lung cancer with 161,000 deaths.
The findings are contained in a new Global Burden of Disease (GBD) study published in The Lancet Public Health, providing a dedicated assessment of second-hand smoke as a global risk factor across 204 countries and territories over 33 years.
The study also raises particular concern for sub-Saharan Africa, where the number of people exposed to second-hand smoke has nearly doubled since 1990.
Although the global proportion of people exposed to SHS has declined, the absolute number remains stubbornly high — and has risen sharply in some parts of Africa.
According to the study, age-standardised exposure fell globally from 43.6 per cent in 1990 to 33.9 per cent in 2023. However, population growth has offset much of that progress, leaving the absolute number of people exposed broadly unchanged.
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In sub-Saharan Africa, however, the number exposed has nearly doubled, highlighting the growing challenge facing governments as the region’s population continues to expand.
The figures are particularly troubling for children, with the study estimating that 767 million children aged 0–14 were exposed to second-hand smoke worldwide in 2023.
Children accounted for more than 12 per cent of the total SHS-attributable health burden, with lower respiratory infections responsible for the greatest burden.
The researchers found that young children are most often exposed in private settings, particularly homes and vehicles, where legislation is limited. Children’s exposure is also closely linked to parental and peer smoking.
The implications are significant for a region with a rapidly growing population. As more people are added to the population, even declining exposure rates can translate into more people breathing tobacco smoke and potentially suffering its consequences.
Women are another major casualty of the problem. Of the 2.71 billion people exposed globally in 2023, 1.49 billion were women.
The researchers said women can face disproportionate exposure in settings where smoking is concentrated among men, particularly through household smoking.
The study said this gender disparity reflects, among other factors, high rates of male household smoking and the limited ability of some women to enforce smoke-free rules in private spaces.
Beyond the number of deaths, the study found that ischaemic heart disease generated the largest health loss associated with second-hand smoke, accounting for an estimated 12 million DALYs in 2023.
The finding reinforces growing evidence that exposure to second-hand smoke is not merely a nuisance or an issue of indoor air quality but a significant cardiovascular health risk.
The researchers said stronger implementation and enforcement of comprehensive smoke-free legislation must be accompanied by measures such as tobacco taxation, marketing restrictions, plain packaging and smoking-cessation programmes.
The study cautioned that its estimates are subject to uncertainty, particularly in low- and middle-income countries where data on SHS exposure are more limited.
Much of the available exposure information is self-reported, while the analysis does not include exposure to electronic nicotine-delivery systems, heated tobacco products or third-hand smoke.
With the number of people exposed to second-hand smoke in sub-Saharan Africa having nearly doubled since 1990, the study makes a compelling case for governments to intensify tobacco-control measures and strengthen protection for non-smokers.
The researchers declared that sustained enforcement of comprehensive smoke-free laws, coupled with broader efforts to reduce active smoking, will be essential to translating declining exposure rates into real reductions in disease and premature deaths.
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