Just cutting down the number of cigarettes does not reduce smokers' risk of early death
The conclusion was reached by researchers at the Universities of Glasgow and Stirling who examined data from more than 5,200 men and women living in the central belt of Scotland who were smoking when first recruited to two studies in early 1970s.
All of the participants were re-contacted a few years later and asked again about their smoking. Some had stopped altogether, some had reduced the number of cigarettes they smoked, while others had maintained or increased the level of their smoking.
All deaths were logged between the second screening and 2010, enabling the researchers to see whether there was any difference in the mortality rates between the quitters, reducers and maintainers.
The researchers found that, compared to maintainers, the quitters had lower mortality rates, but there was no significant difference between the reducers and the maintainers.
In one of the two studies, a sub-group of the reducers who had been among the heaviest smokers at the start did show lower mortality rates but this was not seen in the other study.
The Scottish findings, published in the American Journal of Epidemiology, do not support those of a similar long-term study in Israel where smoking reduction did appear to reduce mortality rates, but are consistent with larger studies of shorter duration in Denmark and Norway where it did not.
Professor Linda Bauld from Stirling University, one of the paper's authors said: "Our results support the view that reducing the number of cigarettes you smoke is not a reliable way of improving your health in the long term.
"However, what we do now know is that it may have a valuable role as a step toward giving up altogether – through cutting down to quit, an approach that has been recommended in recent guidance in the UK".
The original two studies were: The Collaborative Study, which included 1,524 men and women smokers aged 40–65 years in a working population who were screened twice, in 1970–1973 and 1977; and the Renfrew/Paisley Study which included 3,730 men and women smokers aged 45–64 years in a general population who were screened twice, in 1972–1976 and 1977– 1979. Both groups were followed up through 2010.