Everybody knows smoking is bad for health. Yet why do people keep puffing away and endangering their health? Much research has been carried out on the effects of smoking but none has been as long-term and comprehensive as this. The Copenhagen City Heart Study enlisted more than 8,045 people aged 30 to 60 years in a study to take the spirometry tests which were conducted 25 years apart.

Only those with normal lung function and no history of asthma have been accepted for the study. They comprise 5,280 smokers, 1,513 never-smokers, and 1,252ex-smokers. The results show that the longer people smoke, the higher is their risk contracting chronic obstructive pulmonary disorder (COPD). After 25 years of smoking, at least 25 per cent of smokers have developed clinically significant COPD, while 30 to 40 percent have reduced lung function. Over the period of 25 years, 109 of the 2,912 deaths were from COPD. Out of this, 100 deaths occur in active smokers, seven in ex-smokers and two in non-smokers.

This shows that people who smoke run a higher risk of COPD and the longer people smoke, the higher the risks of developing COPD. In short, long-term smokers are burning their lungs away.