COPD is a slowly progressive airway disease that produces a serious decrease in lung function, which is not fully reversible. A study conducted on participants suffering from the disease (chronic bronchitis or emphysema) showed that those patients who continued to smoke had a significant decline in the lung function as compared to those who ceased to smoke.
The main objective of the study was to find out whether a management plan including smoking cessation and inhaled Bronchodilators could delay the beginning of clinically evident COPD. The study was done on 35-65 years old smokers having mild to moderate impairment in lung function. The participants were categorized into 3 groups: one on smoking cessation and Bronchodilator inhaler (1st group), second on smoking cessation and placebo (no medicine) inhaler (2nd group) and the third on usual care (3rd group).
It was observed from the study that smoking cessation did help to reduce the rate of lung function decline whereas inhaled Bronchodilator did not have any such effect. It was also found that 21% of participants in the 1st and the 2nd group showed a long term success in stopping smoking whereas only 5% of participants in the 3rd group were able to do so.
A follow up study of the participants done after 11 years showed that 16.7% of the participants were able to quit smoking, 57.4% smoked irregularly and 25.9% continued to smoke since the beginning of the study. Out of those who continued to smoke 18.1% had lung function less than 50% and 38% had lung function less than 60% as compared to the predicted normal level (hence indicating severe to moderate COPD). Among those who stopped smoking only 3.3% had lung function less than 50% and 10% had lung function less than 60% as compared to the predicted normal level.
Hence the above study proves that people (suffering from COPD) who continue to smoke can severely impair their lung function, therefore, it is best to quit smoking.