Secondhand smoke has been linked to a significant global burden of heart disease, with ischemic heart disease emerging as the leading cause of deaths attributable to exposure to tobacco smoke, according to a new study published in The Lancet Public Health.
The study estimates that 2.71 billion people worldwide were exposed to secondhand smoke (SHS) in 2023, and exposure was associated with 1.66 million deaths and 44.8 million disability-adjusted life years (DALYs).
Of the deaths attributed to second-hand smoke, ischemic heart disease accounted for the largest proportion, with an estimated 537,000 deaths worldwide in 2023. This was followed by chronic obstructive pulmonary disease with 354,000 deaths, stroke with 278, lower respiratory tract diseases with 185,000, and cancer of the trachea, bronchi and lung with 161,000 deaths.
The findings are contained in a new Global Burden of Disease (GBD) study published in The Lancet Public Health, which provides a targeted assessment of secondhand smoke as a global risk factor in 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 almost doubled since 1990.
Although the global proportion of people exposed to second-hand smoke has fallen, the absolute number remains stubbornly high and has increased markedly in some parts of Africa.
According to the study, age-standardized exposure fell globally from 43.6 percent in 1990 to 33.9 percent in 2023. However, population growth has offset much of that progress, leaving the absolute number of people exposed virtually unchanged.
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However, in sub-Saharan Africa, the number of people exposed has almost doubled, highlighting the growing challenge facing governments as the region’s population continues to expand.
The figures are particularly worrying for children, as the study estimates that 767 million children between 0 and 14 years old were exposed to second-hand smoke worldwide in 2023.
Children accounted for more than 12 percent of the total health burden attributable to SHS, with lower respiratory tract infections responsible for the greatest burden.
Researchers found that young children tend to be exposed most frequently in private settings, especially homes and vehicles, where legislation is limited. Children’s exposure is also closely related to the smoking of their parents and peers.
The implications are significant for a region with a rapidly growing population. As more people join the population, even decreasing exposure rates can result in more people breathing in tobacco smoke and potentially suffering its consequences.
Women are another major victim of the problem. Of the 2.71 billion people exposed worldwide in 2023, 1.49 billion were women.
The researchers said women may 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 smoking in the home and the limited ability of some women to enforce smoke-free rules in private spaces.
Beyond the number of deaths, the study found that ischemic heart disease generated the largest health loss associated with secondhand smoke, accounting for approximately 12 million DALYs in 2023.
The finding reinforces growing evidence that exposure to secondhand smoke is not simply a nuisance or indoor air quality problem, but a significant risk to cardiovascular health.
The researchers said that stricter implementation and enforcement of comprehensive anti-smoking legislation must be accompanied by measures such as tobacco taxes, marketing restrictions, plain packaging and smoking cessation programs.
The study cautioned that its estimates are subject to uncertainty, particularly in low- and middle-income countries where data on SHS exposure is 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 thirdhand smoke.
As the number of people exposed to secondhand smoke in sub-Saharan Africa has nearly doubled since 1990, the study makes a compelling case for governments to step up tobacco control measures and strengthen protections for non-smokers.
The researchers stated that sustained enforcement of comprehensive anti-smoking laws, along with broader efforts to reduce active smoking, will be essential to translate declining exposure rates into real reductions in disease and premature death.
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