Halving the number of cigarettes smoked every day in the belief that it will stave off an early death makes no difference, suggests research in the journal Tobacco Control.
Although reducing consumption may have a place as a temporary measure in smoking cessation, this study proves quite clearly that the only safe way out of the risk caused by smoking is to quit, say the authors.
They base their findings on more than 51,000 men and women, all of whom were aged between 20 and 34 at the start of the study.
Participants were initially assessed for cardiovascular risk factors, and then screened again twice at an interval of three to 10 years, adding up to an average monitoring period of over two decades.
Participants were classified as never smokers; ex smokers, quitters (those who gave up between the first and second check); moderate smokers (1 to 14 cigarettes daily); reducers (more than 15 cigarettes a day, cut by more than half at the second check); and heavy smokers (more than 15 cigarettes a day).
Among men, deaths from lung cancer and cancers associated with smoking were not significantly lower in those who had cut back compared with heavy smokers. But this was not true of women who cut back, where the reverse was true.
And men who cut back only had slightly lower death rates from all causes combined than the heavy smokers during the first 15 years. After that, death rates were comparable.
And there were no significant differences in death rates from specific causes, including early death from cardiovascular disease, among women who cut back their daily consumption, compared with those who continued to smoke heavily.
Women who cut back actually had higher death rates from all causes combined than heavy smokers.
The authors conclude that long term monitoring provides no evidence that heavy smokers, who halve their daily cigarette consumption, significantly cut their risk of early death. They add that people may be misled if they are advised that cutting back will help them stave off disease.