A new study by the Institute for Health Metrics and Evaluation (IHME) has linked exposure to secondhand smoke (SHS) to increases in the risk of developing serious health outcomes including ischemic heart disease, stroke and type 2 diabetes.
When a nonsmoker is affected by SHS, also known as passive smoking, it increases the risk of ischemic heart disease and stroke by a minimum of 8 percent and 5 percent respectively, the study shows.
SHS exposure was associated with at least around 1 percent higher risk of lung cancer.
The IHME-led burden of proof analysis published in Nature Medicine studied the relationship between SHS and detrimental health outcomes such as ischemic heart disease, stroke, type 2 diabetes, lung cancer, ear infection), asthma, lower respiratory infections, breast cancer, and chronic obstructive pulmonary disease.
It found that while progress has been made in reducing smoking rates, SHS remains a threat to nonsmokers, especially children.
In 2021, it is estimated that over 760 million children were exposed to tobacco smoke worldwide.
This research revealed a concerning link between SHS exposure and an increased risk of health issues that commonly affect children, such as asthma, lower respiratory infections, and otitis media (ear infection).
“Despite the weak underlying evidence for these associations, our results reinforce the harmful effects of SHS on health and the need to prioritize advancing efforts to reduce active and passive smoking through a combination of public health policies and education initiatives,” the authors say.
The available evidence of associations between SHS and otitis media, asthma, lower respiratory infections, breast cancer, and COPD are weaker and these risk-outcome pairs were classified as one-star associations.
The risk is bigger for some diseases, like heart disease and cancer, but overall it’s not as strong as other studies have shown.
This might be because the studies they looked at were not perfect, making it hard to ascertain how much SHS hurts.
But even a small risk is bad, especially for serious diseases like heart attack and stroke.
Tobacco use is one of the leading risk factors for disease burden and mortality worldwide, contributing to 229.8 million.
Secondhand smoke exposure is a major tobacco-related public health concern for nonsmokers. Despite a gradual decline in smoking rates over the past half-century, it is estimated that approximately 37 percent of the global population is still exposed to the smoke emitted from the burning end of tobacco products or exhaled from smokers, with higher rates of exposure among women and children compared to men, and evident racial and economic disparities.
This is concerning as tobacco smoke is composed of thousands of chemicals and compounds, including many carcinogens, which when inhaled damage the human body and lead to disease and death.
The 2019 Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) estimated that 1.3 million deaths were attributable to SHS globally in 2019, with the largest burden concentrated in low- and middle-income countries.
These patterns have made SHS a priority for tobacco control efforts, especially after the adoption of the World Health Organization’s Framework Convention on Tobacco Control, a global treaty aimed at implementing evidence-based measures to reduce both active and passive smoking.
The authors say this necessitated an updated summary of the exposure–response relationship between SHS and multiple adverse health outcomes, as well as innovatively quantifying the strength of the evidence supporting these relationships.