A Cochrane review [Abstract] 1 included 10 studies with a total of 3760 subjects. Pharmacotherapy was used as part of the interventions in 3 trials. 5 studies included behavioural support in the intervention, 4 included self-help therapy, and the remaining study had arms which included behavioural support and arms which included self-help therapy. 9 studies reported smoking abstinence at either 6 month follow-up, 12 month follow-up, or both, and the remaining trial reported cigarettes per day over seven days at 6, 9, and 12 month follow-ups. Abstinence was verified in 8 studies, by either expired carbon monoxide, saliva cotinine, saliva thiocyanate, or asking a relative or friend to confirm the participant had stopped smoking. Neither reduction or abrupt quitting had superior abstinence rates when all the studies were combined (RR 0.94, 95% CI 0.79 to 1.13), whether pharmacotherapy was used (RR 0.87, 95% CI 0.65 to 1.22), or not (RR 0.97, 95% CI 0.78 to 1.21), whether studies included behavioural support (RR 0.87, 95% CI 0.64 to 1.17) or self-help therapy (RR 0.98, 95% CI 0.78 to1.23).
A meta-analysis 2 included 3 high-quality RCTs involving a total of 1607 subjects. The participants were adult smokers who were addicted to tobacco, defined as those who smoked at least 15 cigarettes or 12.5 grams of loose-leaf tobacco daily or who had an end-expiratory carbon monoxide concentration of at least 15 ppm. Both groups used an equal amount of nicotine replacement therapy (NRT) before and after quitting smoking. The outcome measures were the prolonged and 7-day CO-verified abstinence rates. The prolonged abstinence rate of the gradual cessation group was significantly lower than that of the abrupt group (RR 0.77, 95% CI 0.68 to 0.98; I²=36%). The result of 7-day smoking cessation rate was also lower in the gradual group (RR 0.76 95% CI 0.61 to 0.94; I²=39%).
<para><emphasis>Comment:</emphasis> The quality of evidence is downgraded by heterogeneity. </para>
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