Can smokers be helped to reduce harm by smoking fewer cigarettes or using different tobacco products

People who smoke may be unwilling or unable to stop smoking completely. Cutting down the number of cigarettes smoked daily or smoking less damaging products may reduce the harm caused by smoking. It may also be a step towards stopping smoking completely. This approach might, however, undermine the importance of quitting which has very clear health benefits. We found 16 controlled trials that tested ways to help people to cut down the number of cigarettes they smoked. We found three randomized controlled trials which tested the effects of using products designed to reduce damage, such as Potentially Reduced Exposure tobacco Products (PREPs). Eleven of the trials tested nicotine replacement therapy (NRT) as an aid to cutting down. Our combined analysis of nine of these trials (3429 smokers) found that nicotine replacement roughly doubled the odds of reducing the number of cigarettes per day by 50% or more. However, levels of carbon monoxide and cotinine (markers within the body of exposure to tobacco smoke) did not reduce by the same proportion. This suggested that there may not be a direct relationship between the reduction in number of cigarettes and the reduction in harmful effects. Although NRT helped significantly more people to cut down, few were able to sustain the reduction over time. NRT also nearly doubled the odds of quitting completely. One trial failed to find a benefit of bupropion either for cutting down or for quitting. Four trials tested advice or instructions for reducing the number of cigarettes smoked per day, and did not find clear evidence of a significant effect. We did not find any trials which reported the long-term effects on health of cutting down, and it remains uncertain how much health benefit there is from cutting down.