Compared to the control , both interventions appeared to be effective among hookah smokers ( RR = 2.5 ; 95 % CI = 1.3-4 .7 and RR = 2.2 ; 95 % CI = 1.3-3 .8 , respectively ) but less effective among cigarette smokers ( RR = 6.6 ; 95 % CI = 4.6-9 .6 and RR = 5.8 ; 95 % CI = 4.0-8 .5 ) , respectively .