According to British and Danish researchers the longer someone smokes the higher their risk of developing the incurable lung condition chronic obstructive pulmonary disease (COPD).
The researchers say that at least a quarter of long-term smokers will develop the incurable lung disease which includes a range of conditions, including bronchitis and emphysema, which make it difficult to breathe.
It does not include other obstructive diseases such as asthma.
COPD is the fourth leading cause of death in America and the sixth most common cause of death in Britain.
It claimed the lives of 122,283 Americans in 2003 and kills more than 30,000 Brits each year and what is more the number of women dying from the disease has surpassed the number in men.
In 2004, 11.4 million U.S. adults were estimated to have COPD but as many as 24 million U.S. adults have evidence of impaired lung function, suggesting it is under-diagnosed.
Between 600,000 and 900,000 people in the UK have been diagnosed with COPD and an estimated 13.3% of Britons over 35 possibly have features of it.
Smoking is the primary risk factor for COPD and up to 90 percent of COPD deaths are caused by smoking.
Female smokers are nearly 13 times as likely to die from COPD as women who have never smoked, while male smokers are nearly 12 times as likely to die from COPD as men who have never smoked.
Other risk factors include air pollution, second-hand smoke, history of childhood respiratory infections and heredity factors.
Occupational exposure to certain industrial pollutants also increases the odds for COPD.
The study examined information on over 8,000 people aged 30 to 60 over a 25 year period and all lived in or around Copenhagen; 5,280 were smokers, 1,513 had never smoked and 1,252 were ex-smokers.
By the end of the study, the researchers found that at least 25% of the smokers without any initial symptoms of the disease had "clinically significant" COPD, while up to 40% had some signs of the condition.
Over the 25 year period, 2,900 people died, 109 of those from COPD and nine out of 10 of those were smokers at the start of the study, while just two non-smokers died of the disease.
While the risk of COPD was reduced in those who gave up smoking early on in the study, none of the ex-smokers developed severe COPD and only seven died.
The lungs of almost all the male non-smokers continued to function well to the end of the period but this was only the case in six out of 10 of those who continued smoking.
Nine out of 10 female non-smokers had lungs that functioned well at the end of the study compared with only seven out of 10 female smokers.
The researchers, led by Dr Peter Lange of Hvidovre Hospital, Hvidovre, Denmark, say the main finding is quite simple - the longer people smoke, the higher the risk of developing COPD.
Experts say the message is clearly that many smokers develop airway obstruction if they live long enough and continue to smoke and the study should act as yet another wake-up call to smokers to get their lungs tested and to get help to stop.