Effects of smoking on lung function
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Smoking and Lung Function Decline
Smoking and Reduced Lung Function in Adults
Smoking is strongly linked to a decline in lung function, as shown by lower forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) in both current and former smokers compared to never-smokers. The decline is more pronounced in current smokers, especially those with high smoking intensity, and the effect is dose-dependent—the more someone smokes, the greater the reduction in lung function. Even low-intensity smokers and former smokers experience a faster decline in lung function than never-smokers, and this accelerated decline can persist for decades after quitting smoking Tian2023Oelsner2019.
Smoking and Lung Function in Asthma
Among adults with newly diagnosed asthma, regular and former smoking are associated with significantly reduced lung function, including both large and small airways. The reduction in FEV1 is notable in regular smokers and those who recently quit, but not in occasional smokers or those who quit over a year ago. A clear dose-response relationship exists: higher daily smoking rates and greater lifetime exposure lead to greater lung function impairment. In adult-onset asthma, a history of smoking 10 or more pack-years predicts a faster decline in FEV1 and FVC Tommola2016Jaakkola2019. However, quitting smoking can lead to significant improvements in lung function and reduced airway inflammation within weeks, highlighting the benefits of cessation even after asthma diagnosis .
Smoking Effects in Adolescents and Early Life
Adolescent smoking is linked to mild airway obstruction and slower growth of lung function, with girls possibly being more vulnerable than boys. Smoking five or more cigarettes a day is associated with slower growth in FEV1 and other lung function measures. Girls who smoke may even experience a decline in lung function during late adolescence, while non-smoking girls reach a plateau. Maternal smoking during pregnancy and adolescent smoking both contribute to reduced FEV1/FVC ratios and increased airway resistance at age 16, indicating early and lasting effects on lung health Gold1996Thacher2018.
Early-Life Exposures and Smoking
Early-life exposures, such as lower respiratory infections and home overcrowding, can further worsen the negative impact of smoking on adult lung function. Smokers with these early-life exposures have greater deficits in FEV1 and FVC in midlife compared to never-smokers, suggesting that smoking can amplify the effects of early lung insults and prevent recovery from earlier deficits .
Biological Mechanisms: Smoking and Lung Immune Cells
Cigarette smoke disrupts the function of alveolar macrophages, the immune cells responsible for defending the lungs. Smoking impairs their ability to clear pathogens and maintain lung homeostasis, which contributes to chronic lung disease and increases susceptibility to infections and further lung injury .
Broader Health Risks and Passive Smoking
Smoking increases the risk of chronic respiratory diseases such as COPD, lung cancer, and asthma. Passive smoke exposure also reduces lung function in children and increases the risk of respiratory infections and asthma. Both active and passive smoking are linked to a higher risk of tuberculosis and sleep apnea .
Conclusion
Smoking causes significant and lasting damage to lung function in both adults and adolescents, with effects that are dose-dependent and can persist long after quitting. Early-life exposures can worsen these effects, and even low levels of smoking are harmful. Quitting smoking, however, can slow or partially reverse lung function decline, especially in people with asthma. These findings underscore the importance of smoking prevention and cessation for protecting lung health at all ages.
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