By the association of nicotinic acetylcholine receptors in the brain, nicotine in the therapeutic window lowers neuronal damage and raises protective factors. These data, however, are contradicted by other findings. Here, we assessed the effects of transdermal nicotine administration on cognitive functions in healthy non-smoker adults by systematic review and meta-analysis of clinical trials.
We included reports of clinical trials comparing the effects of nicotine patches with placebo in healthy non-smoking adults. The main outcome was the impact of nicotine patches on overall cognitive function with a focus on attention and memory. Standard meta-analytic and statistical methods measured the effect of transdermal nicotine compared with placebo patches.
We included 31 publications involving 978 subjects. Nicotine patches boosted cognitive function in healthy adults (0.233 SMD, 95%CI, 0.111–0.355, p < .001). Overall heterogeneity of the studies was found to be modest (ϰ2 = 68.24, T2 = 0.07, I2
= 50.17%, p < .001). Also, nicotine patches improved attention (0.231 SMD, 95%CI, 0.106–0.356, p < .001). We found the inter-study heterogeneity to be low (ϰ2 = 40.95, T2 = 0.03, I2
= 34.07%, p = .042). Further, the enhancement of memory by transdermal nicotine did not reach statistical significance in normal subjects (0.270 SMD, 95% CI, −0.293–0.833, p = .347). Also, high inter-study heterogeneity was found among studies (ϰ2 = 27.25, T2 = 0.43, I2
= 77.98%, p < .001).
The meta-analysis showed that transdermal nicotine had statistically significant positive effects on attention, and non-significant effects on memory, in healthy non-smoking adults. The results encourage further studies of the therapeutic potential of nicotine patches in disorders of cognition.