Prediction of abstinence at 10 weeks based on smoking status at 2 weeks during a quit attempt: secondary analysis of two parallel, 10-week, randomized, double-blind, placebo-controlled clinical trials of 21-mg nicotine patch in adult smokers.
BACKGROUND
Smoking cessation outcomes are calculated as the probability of abstinence at follow-up among all enrolled smokers, but it is also useful to estimate the probability of success for those who experienced success or failure at earlier time points.


OBJECTIVE
The primary aims were to estimate the probability of maintaining abstinence through week 10 among subjects who were abstinent at week 2, and to assess the effect of active treatment with a nicotine patch. We also examined outcomes at week 6 and, among subjects who smoked during the first 2 weeks of treatment, the probability of reestablishing abstinence later, as well as the effect of active treatment on this outcome.


METHODS
We analyzed pooled data from 2 previously published, parallel, double-blind studies in which subjects were initially randomized to receive an active nicotine patch (starting at 21 mg) or a placebo patch. Subjects randomized to active treatment followed a double-blind step-down dosing regimen: 24-h/21-mg patches for the first 6 weeks of treatment, followed by 14- and 7-mg patches for successive 2-week periods. Biochemically verified abstinence (exhaled carbon monoxide <or=8 ppm) was assessed during laboratory visits.


RESULTS
Most subjects were white (94.8%) and female (61.6%), with a mean (SD) age of 43.1 (10.2) years. Subjects had been smoking for a mean of 24.5 (10.2) years and smoked a mean of 30.6 (10.4) cigarettes per day. In both the nicotine (n = 249) and placebo (n = 253) groups, all subjects who were abstinent during the first 2 weeks had a high probability of maintaining abstinence through week 10, but subjects treated with the active patch were significantly more likely to remain abstinent (active: 79.8% [67/84], placebo: 52.6% [20/38]; relative risk [RR] = 1.52 [95% CI, 1.10-2.09]). Also, at week 6, subjects receiving active treatment had a greater chance of remaining abstinent (active: 94.3% [82/87], placebo: 78.0% [32/41]; RR = 1.21 [95% CI, 1.02-1.43]). To assess the effect of treatment on recovery from smoking lapses, we examined the probability of abstinence during week 10 among subjects who smoked during the first 2 weeks of treatment. Among them, treatment was associated with a greater probability of later success: 31.4% (50/159) of those treated with the active patch and 12.5% (26/208) of those receiving placebo were abstinent at week 10 (RR = 2.52 [95% CI, 1.64-3.85]). Similar results were observed at week 6 (49.4% [80/162] vs 21.2% [45/212]; RR = 2.33 [95% CI, 1.72-3.15]).


CONCLUSIONS
More than two thirds (71.3%) of subjects who were abstinent 2 weeks into a quit attempt maintained that abstinence through the end of 10 weeks of treatment. Use of a nicotine patch was significantly associated with maintaining abstinence and with recovering abstinence after an early lapse.
Ferguson
Stuart G
SG
Pinney Associates, Inc., Pittsburgh, Pennsylvania 15213, USA. sferguson@pinneyassociates.com
Gitchell
Joseph G
JG
Shiffman
Saul
S
Sembower
Mark A
MA
D000279:Administration, Cutaneous; D000328:Adult; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009538:Nicotine / Q000008:administration & dosage / Q000627:therapeutic use*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000627:therapeutic use*; D016032:Randomized Controlled Trials as Topic; D012008:Recurrence; D016540:Smoking Cessation / Q000379:methods* / Q000706:statistics & numerical data; D000074606:Smoking Prevention; D013997:Time Factors; D016896:Treatment Outcome
D018722:Nicotinic Agonists; D009538:Nicotine