The paper by West and Zhou published in this issue of Thorax (see page 998) is an important contribution to the literature because it addresses and refutes the questions raised, on the basis of retrospective case-control studies, about the effectiveness of nicotine replacement therapy (NRT) in “real world” settings.1 2 Contrary to those retrospective analyses, West and Zhou’s prospective population study found that NRT helps smokers to quit, roughly doubling the odds of successful quitting. The odds ratio of 2.2 reported by West and Zhou is quite consistent with the odds ratios reported in randomised clinical trials.3

In this sense, West and Zhou’s finding that NRT is effective should come as no surprise. The efficacy of NRT has been demonstrated in over 100 randomised controlled trials encompassing over 35 000 smokers.3 Moreover, the effectiveness of NRT has also been demonstrated in multiple trials that tested NRT under over-the-counter conditions.4 These studies not only showed that over-the-counter NRT was more effective than placebo, but also …