Quitting smoking for 2+ years lowers depression risk in COPD patients: Seoul St. Mary's Hospital

Patients with chronic obstructive pulmonary disease, or COPD, who maintain abstinence from smoking for more than two years face a lower risk of developing depression than those who continue to smoke, a new study has found. The risk reduction was particularly pronounced among patients with severe COPD, at about 60 percent.

The Catholic University of Korea's Seoul St. Mary's Hospital said Friday that its research team analyzed the link between smoking cessation duration and depression risk among newly diagnosed COPD patients. The joint research was led by Professor Shin Hyun-young of the hospital's Department of Family Medicine and Professor Park Sang-min of Seoul National University Hospital's Department of Family Medicine.

COPD is a chronic respiratory disease in which the airways narrow and airflow becomes persistently restricted, caused by factors such as smoking and fine dust. Depressive symptoms are reported to accompany COPD in 20 to 60 percent of patients, and the combination of smoking and depressive symptoms can raise the risk of death even further.

Using health checkup data from the National Health Insurance Service, the research team analyzed 5,671 adults newly diagnosed with COPD between 2003 and 2014. Over an average follow-up period of eight to nine years, 603 of them developed depression for the first time.

The team divided participants into four groups based on their smoking status before and after diagnosis. The groups were: continuing smokers, those who quit for less than two years after diagnosis, those who abstained for two years or longer, and those who had never smoked.

The long-term quitters had a 34 percent lower risk of developing depression than those who kept smoking. Among the 579 long-term quitters, 35 developed depression, for an incidence rate of 8.4 per 1,000 person-years — meaning roughly 8.4 cases per 1,000 patients annually. Among the 1,138 continuing smokers, 114 developed depression, for a rate of 12.0 per 1,000 person-years.

By contrast, those who quit for less than two years showed no statistically significant difference in depression risk compared with continuing smokers. Non-smokers also showed no significant difference.

Among all COPD patients, the study confirmed a significant risk reduction only in those who had abstained from smoking for two years or longer. The association was even stronger among patients with more severe disease.

In a separate analysis limited to patients with severe COPD, long-term quitters had about a 60 percent lower risk of depression than continuing smokers. The association remained statistically significant among men and patients under 65. It also held among those with fewer coexisting conditions, higher income levels, and a body mass index under 25 kilograms per square meter.

The research team said nicotine affects the release of neurotransmitters such as dopamine and serotonin, as well as the body's stress hormone system. Maintaining abstinence over the long term may allow neurotransmitter balance to recover and inflammation in the body to subside. They added that withdrawal symptoms during the first two years of quitting may mean the brain and body need time to recover.

"A COPD diagnosis can be an important turning point for patients to change their lifestyle," said Park Sang-min, professor of family medicine at Seoul National University Hospital. "This study shows that not just attempting to quit smoking, but sustaining it consistently, carries positive implications for mental health as well."

"The effect of smoking cessation was especially pronounced among patients with severe COPD," said Shin Hyun-young, professor of family medicine at Seoul St. Mary's Hospital. "We hope this research can serve as medical evidence for combining smoking cessation counseling with mental health management in the treatment of COPD patients."

The findings were published in the September issue of the international journal Respiratory Medicine.

Meanwhile, according to the Korea Disease Control and Prevention Agency's National Health Information Portal, an estimated 3 million people in South Korea have COPD. That figure represents about 13 percent of adults aged 40 and older. However, only 2.8 percent of them have been formally diagnosed by a doctor, and just 1.6 percent are receiving treatment.