Nationwide study of chronic codeine use and its impact on cough related diseases in South Korea.

Codeine is widely used to control coughs, although concerns about its overuse arise due to its side-effects. This study aimed to evaluate the status of codeine usage according to various medical conditions. The Korean National Health Insurance Service sample cohort was analyzed. Subjects with more than continuous sixty days of antitussive and codeine were defined as chronic users. It was evaluated according to age, smoking status, chronic obstructive pulmonary disease (COPD), asthma, allergic rhinitis (AR), bronchiectasis, chronic cough (CC), gastroesophageal reflux disease (GERD), and lung cancer. A total of 89,289 chronic antitussive users were identified, of whom 589 were chronic codeine users. The chronic codeine users were older, more likely to be smokers, and more likely to have multimorbidity (P < 0.001, all). After adjusting age, chronic codeine use showed a positive correlation with lung cancer (adjusted odds ratio [aOR]: 6.99), COPD (aOR: 2.04), GERD (aOR: 1.93), and CC (aOR: 1.60). Multimorbidity also revealed positive correlations, increasing as the number of comorbidities rose (P < 0.001). Our findings highlight that chronic codeine usage is associated with underlying cough-inducing diseases, emphasizing the need for monitoring and guidelines to ensure safer use, especially among older adults and those with chronic respiratory conditions.