COPD Poses Public Health Risk for US Smokers, Nonsmokers

Chronic obstructive pulmonary disease (COPD) remains a significant public health challenge in the US among current smokers, ex-smokers, and never smokers alike, according to a study published in Tobacco Induced Diseases.

Although it is the primary risk factor, the researchers explained that smoking is not the sole determinant of COPD; data from 2019 found that nonsmokers make up about one-third of the 391.9 million people between the ages of 30 and 79 years with COPD worldwide. Other notable risk factors include air pollutants, biomass fuels, and a history of respiratory infections.

Consequently, the researchers emphasized the importance of investigating COPD among smokers and never-smokers worldwide. However, there remains limited knowledge about COPD prevalence and mortality among both groups. Because of this, they conducted a study to examine the prevalence of COPD and its associated risk factors among US smokers and never-smokers between the ages of 20 and 79; the researchers also investigated the all-cause mortality among these groups.

While smoking is a key risk factor for chronic obstructive pulmonary disease (COPD), significant prevalence also exists among non-smokers. | Image Credit: Nopphon - stock.adobe.com

To do so, they used data from the National Health and Nutrition Examination Survey (NHANES), which encompasses health measurements obtained at mobile examination centers (MECs) and interviews conducted in respondents’ homes. More specifically, the researchers utilized patient data from 10 successive NHANES survey cycles, spanning 1999 to 2018.

Patients were categorized as smokers or never-smokers based on how they answered the question, “Have you smoked at least 100 cigarettes in your entire life?” Smoking status was further assessed with the question, “Do you now smoke cigarettes?”, categorizing those who responded with “every day” or “some days” as current smokers and those who responded “not at all” as ex-smokers. Additionally, patients were considered to have COPD if they answered yes to the question, “Has a doctor or other health professional ever told you that you had emphysema/chronic bronchitis/COPD?”

As for follow-up, the researchers cross-referenced the NHANES data with death records in the National Death Index (NDI) from 1999 to December 31, 2019, to analyze the primary outcome measure: all-cause mortality. Each participant’s follow-up period was defined as the duration between their NHANES baseline examination and the date of either their death or last follow-up visit (December 31, 2019).

The study population consisted of 50,773 patients. Of these patients, 11,257 were identified as current smokers, 11,865 as ex-smokers, and 27,651 as never-smokers. The researchers identified COPD diagnoses in 12.59% (n = 1374) of current smokers, 9.61% (n = 1210) of ex-smokers, and 4.14% (n = 1109) of never-smokers.

They noted that the proportions of current smoking-related COPD (62.2%), ex-smoking-related COPD (51.1%), and never smoking-related COPD (75%) were higher in female patients. Similarly, among never-smokers, female patients with COPD (75%) outnumbered male patients (25%) by 3 times. Additionally, non-Hispanic White patients exhibited a higher proportion of COPD among current smokers (78.9%), ex-smokers (81.4%), and never-smokers (70.3%).

From 1999 to 2018, the distribution of smoking status nationwide underwent significant changes, with the amount of current smokers declining and never-smokers increasing. Additionally, there was a higher COPD prevalence rate among current smokers between 1999 and 2018, rising from 13.7% (n = 96) in 1999 to 21.9% (n = 192) in 2018.

In comparison, COPD prevalence among ex-smokers remained relatively stable at 10.1% in both 1999 (n = 115) and 2018 (n = 180). Conversely, the COPD prevalence of never-smokers declined from 4.9% in 1999 (n = 321) to 3.3% (n = 493) in 2018. Also, the researchers identified independent COPD risk factors across all groups, including being female, of older age, and having a lower income; US citizens and non-Hispanic White patients, in particular, were at higher COPD risk.

Lastly, the median follow-up period was 114 months (IQR, 62-171.25). During this time, the observed mortality rates were 21.1% among current smokers with COPD, 29% among ex-smokers with COPD, and 12% among never-smokers with COPD.

The researchers acknowledged their limitations, one being that COPD diagnoses were based on self-reported information and not validated through medical records. Therefore, recall biases, social expectations, and proxy response biases may have impacted the accuracy of COPD prevalence estimates. Despite this, they expressed confidence in their findings and suggested areas for further research.

“The findings underscore that COPD continues to pose a significant public health challenge across these groups,” the authors concluded. “Furthermore, the study emphasizes the critical importance of early detection and intervention in managing COPD, warranting further investigation into effective public health strategies.”

References

1. Li X, Xue M, Xu D, Fan C, Zhang J. Prevalence, mortality and risk factors for self-reported COPD among smokers and never smokers, NHANES 1999-2018. Tob Induc Dis. 2024;22:10.18332/tid/192745. doi:10.18332/tid/192745
2. About NHANES. CDC. Reviewed May 31, 2023. Accessed September 26, 2024. https://www.cdc.gov/nchs/nhanes/about_nhanes.htm