Reduced ability of the lungs to work properly -- a process accelerated by smoking -- increases the risk of death from all causes, shows research in Thorax.
But even giving up smoking for a while halts the decline and can reduce the risk of death from all causes by around 20 per cent, the study shows.
The research involved a long-term study between 1959 and 1989 of over 1,000 men, with additional data on death rates up to the millennium. The men, from two rural areas in Finland with minimal pollution, were part of the large international Seven Countries Study. They were all aged between 40 and 59 in 1959 and were followed up five times over the next 30 years.
People who never smoked lost less of their lung function in later life than those who continued to smoke, and the decline was significantly slower. But this was also true of people who had given up smoking either temporarily or permanently.
The risk of death from all causes was 20 per cent higher in continuous smokers. The findings also show that people who survived longer, whether smokers or non-smokers, tended to have lost less of their lung function than those who died.
The authors suggest that continual stimulation of inflammatory responses in the lungs as a result of smoking may be the critical factor because of the profound functional and anatomical changes this may cause. And they add that preserving as much lung function as possible in later life seems to be linked to a longer life.
(Reference: Smoking cessation, decline in pulmonary function and total mortality: a 30 year follow up study among the Finnish Cohorts of the Seven Countries Study Thorax 2001; 56: 703-7)