How much does relapse after one year erode effectiveness of smoking cessation treatments? Long term follow up of randomised trial of nicotine nasal spray

Abstract
A total of 227 heavy smokers entered the trial; 116 were given the nicotine spray and 111 the placebo. Of these, 47 sustained abstinence from smoking for 1 year. They constituted the long term follow up group; 33 were in the nicotine group, 14 in the placebo group. Criteria for long term sustained abstinence were the same as for the first year. Since the follow up was completed mainly over a 2 month period, the time interval from randomisation varied according to when the smoker entered the trial over 15 months. Standard survival methods were used to analyse the data. Survival times of those who were not contacted beyond 1 year (3 subjects in the nicotine group, 2 in the placebo group) and those who had successfully given up were censored at their last follow up. The Kaplan-Meier method was used to estimate cumulative abstinence up to 31/2 years.