The risk of developing chronic obstructive pulmonary disease (COPD) increased in young people who smoke cigarettes more frequently, indicating smoking is an important COPD risk factor.
Although COPD prevalence increases with age, individuals younger than 50 years can also develop COPD. The researchers explained that, in 2019, an estimated 49.3 million people aged 30 to 39 years had COPD worldwide, which equated to a prevalence of about 4% (3.8% in those aged 30-34 years and 4.9% in those aged 35-39 years). They also noted that cigarette smoking, which is one of the main risk factors for COPD, has recently increased among young Americans due to e-cigarette usage.
Despite these findings, the researchers explained that smoking’s impact on COPD development in young patients remains unclear due to past studies’ limitations, including inadequate cohort populations. Because of this, the researchers conducted a study to evaluate whether smoking is a considerable risk factor for COPD development in patients younger than 40 years.
The researchers used the Korean National Health Information Database (NHID) to create their study population. Formed by the National Health Insurance Service, the NHID provides health checkups, sociodemographic data, and mortality for the Korean population. It also records demographics, medical treatment and claims information, and long-term care insurance.
They utilized NHID medical claims for patients aged 20 to 39 years who participated between 2009 and 2012, later searching through December 2019, with newly diagnosed COPD. Patients with newly diagnosed COPD had International Classification of Diseases, Tenth Revision codes for COPD (J44.x) or emphysema (J43.x), except for J43.0. They also had insurance claims for these codes more than 3 times a year for at least 2 years.
The researchers identified smokers through lifestyle information collected from self-reported questionnaires facilitated at health checkups. The questionnaires helped researchers learn about patients’ daily smoking status, physical activity, alcohol consumption, daily smoking amount, and smoking duration; they defined a former smoker as someone who had smoked at least 100 cigarettes or cigars during their lifetime but did not smoke at the time of health checkup.
As a result, they found 13,789 eligible patients with newly developed COPD. The mean age of participants was 30.84 years, and those with COPD were significantly older than those without; the mean (SD) age of those with COPD was 32.6 (4.72) years, whereas the mean (SD) age of those without COPD was 30.84 (5.00) years (P < .0001). Men accounted for 59.21% of the population and made up a larger proportion of patients with COPD (63.13%).
Within the COPD group, 5626 (40.8%) were current smokers and 1536 (11.14%) were former smokers. Of the population, about 70% of men and 10% of women had a smoking history. In terms of sex, the researchers noted that female smokers had a higher incidence and risk of developing COPD. Age, alcohol consumption, asthma history, and body mass index also showed significant associations between COPD development and smoking status.
The researchers explained that nonsmokers were least likely to develop COPD and current smokers were at the highest risk. Nonsmokers had a COPD incidence rate of 0.2288 per 1000 person-years (PY), compared with 0.2862 per 1000 PY in former smokers and 0.3063 per 1000 PY in current smokers.
Compared with nonsmokers, “the risk of developing COPD was higher in former smokers (adjusted hazard ratio [AHR], 1.208; 95% CI, 1.135-1.285) and the highest in current smokers (AHR, 1.460; 95% CI 1.394-1.529),” the authors wrote.
Additionally, they noted that COPD incidence increased with the smoking amount, as it was highest in those with 20 or more pack-years (AHR,2.24), lower for those with10 to 20pack-years (AHR, 1.55), and lowest for those with less than 10 pack-years (AHR, 1.27).
The researchers also acknowledged their study’s limitations. They explained that COPD diagnosis was based on health insurance claims, and lung function could not be evaluated because of gaps in the original data. Similarly, the researchers could not obtain every potential risk factor for COPD development from the database.
These limitations did not take away from their findings, which they hoped would spur future efforts to prevent young patients from smoking cigarettes and e-cigarettes.
“Our findings suggest that active case findings and smoking cessation policies are also important for proper management and prevention of COPD in young individuals,” the authors concluded.
Chung C, Lee KN, Han K, Shin DW, Lee SW. Effect of smoking on the development of chronic obstructive pulmonary disease in young individuals: a nationwide cohort study. Front Med (Lausanne). 2023;10:1190885. doi:10.3389/fmed.2023.1190885