The number of deaths attributable to second hand smoke exposure has increased between 1990 and 2019

In a recent study posted to the SSRN* preprint server, researchers estimated the prevalence of and assessed trends in exposure to second-hand smoke (SHS) and potential drivers of its health outcomes between 1990 and 2019 globally.

Study: Second Hand Smoke Prevalence and Attributable Disease Burden in 204 Countries and Territories, 1990–2019: A Systematic Analysis from the Global Burden of Disease Study 2019. Image Credit: yamasan0708/Shutterstock.com

*Important notice: SSRN publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Background

Passive smoking has led to a considerable number of fatalities and healthy life years loss among individuals of all ages globally.

The World Health Organization (WHO) has advised all nations to create smoke-free environments and protect individuals from the negative health effects of passive smoke, such as elevated risks of ischaemic heart disease (IHD), chronic obstructive pulmonary disease (COPD), respiratory tract infections, stroke, and otitis media.

Timely access to the prevalence rates of second-hand smoke and related health effects is required to determine appropriate intervention strategies across nations, demographic groupings, and development levels.

About the study

In the present study, researchers used the 2019 Global Burden of Disease (GBD) Study data to update second-hand exposure prevalence and associated health burden by age and sex across 204 nations and territories between 1990 and 2019.

They also decomposed probable drivers of passive smoke-related health burden with time concerning population age, size, and the number of deaths.

The team documented second-hand smoke prevalence and its alterations by gender, sociodemographic index (SDI), and year between 1990 and 2019. Pairs of risks and outcomes were analyzed across ages to estimate SHS-related disease burden, as evaluated based on mortality counts and the disability-adjusted life years (DALYs).

The team utilized the decomposition approach to attribute alterations in any-cause SHS-related DALYs or deaths to public growth, aging, and changes in mortality counts.

Data were searched in the PubMed database for studies published between January 1, 1990, and June 20, 2023. SHS exposure was described in GBD 2019 as non-smoking individuals with tobacco-smoking household contacts instead of using questions investigating second-hand smoke exposure in surveys. Individuals who smoked occasionally or had prior smoking history were deemed non-smokers.

In the GBD study 2019, the SHS-associated disease burden included otitis media among pediatric individuals aged up to 14 years; and cancers involving the trachea, bronchi, and lungs, COPD, ischemic stroke, IHD, subarachnoid and intracerebral hemorrhage, diabetes, and breast cancer for individuals aged ≥25.0 years; and infections of the lower respiratory tract (LRIs) across ages.

The relative risks for diabetes, breast malignancy, and otitis media were obtained from meta-analyses. In contrast, the relative risks for other illnesses were calculated using integrated exposure-response (IER) curves for a PM2.5 level of air pollution.

GBD stud’s population attributable fraction (PAF) was utilized to evaluate the disease burden based on exposure and relative risks.

Disease burden indices included DALYs, deaths, summary exposure values (SEV), the age-standardized DALYs rate (ASDR), and the age-standardized mortality rate (ASMR), with Global Health Data Exchange (GHDx) numbers.

Results

The team identified eight studies that estimated global SHS prevalence and related disease burden. In 2019, worldwide, the age-standardized prevalence rates of second-hand exposure were 31% for men and 45% for women, with percent changes of -0.1 and -0.1, respectively, from 1990 onward.

The nations with the most passive smokers were predominantly high-to-middle-SDI nations for men and low-to-middle- and middle-sociodemographic index nations for women.

Additionally, there were decreasing trends among high-SDI nations and increasing trends among low-to-middle SDI nations from 1990 to 2019. From 1990 to 2019, South Africa, Mexico, Madagascar, Ecuador, and the United States (US) showed the quickest annual SHS reduction rates.

In contrast, there were significant increases in Niger, Mali, El Salvador, Montenegro, and Ghana. Uganda and Bulgaria showed the largest upward and downward trends, respectively.

Among men, SHS exposure was the most prevalent in Greenland, Montenegro, Papua New Guinea, North Macedonia, and Kiribati, with prevalence rates of 51%, 51%, 50%, 49%, and 50%, respectively.

Among women, SHS was highly prevalent in Vietnam, Indonesia, Papua New Guinea, China, and Kiribati, with prevalence rates of 69%, 75%,66%, 63%, and 64%, respectively. In 2019, 2,832 million individuals globally were exposed to passive smoke, among whom 60% were women.

Further, about 1.3 million deaths and 37.0 million DALYs were associated with second-hand smoke exposure, 50% of which were in India and China or among women.

IHD (31%), COPD (22%), and LRIs (13%) were the main causes of second-hand smoke-associated deaths, most commonly among individuals aged below five years for lower respiratory infections, individuals aged between 70.0 and 74.0 years for ischaemic heart disease, and between 80.0 and 84.0 years for chronic obstructive pulmonary disease, respectively.

From 2010 onwards, second-hand smoke-associated DALYs were elevated by <10% since noteworthy reductions in second-hand smoke-associated mortality changes counteracted the effects of public growth and age; however, passive smoke-associated death counts significantly rose in all SDI nations due to the growing and aging population, despite reductions in SHS-associated mortality change.

Conclusion

Overall, the study findings showed that while second-hand smoke exposure prevalence was reduced in most nations, associated mortality increased with increased population and aged individuals from 2010 onwards.

The study findings underscored the need to implement smoke-free regulations on a global scale.

*Important notice: SSRN publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Pooja Toshniwal Paharia

Dr. based clinical-radiological diagnosis and management of oral lesions and conditions and associated maxillofacial disorders.