When participants were analyzed by subgroups according to cigarette consumption , the abstinence rates among smokers who smoked more than 29 cigarettes per day at 12 weeks ( OR 1.39 ; 95 % CI 1.2 to 2.5 ) and 24 weeks ( OR 1.46 ; 95 % CI 1.2 to 2.8 ) were significantly higher in the combination group .