A systematic review and meta-analysis of the effects of mastication on sustained attention in healthy adults.

The aims of this paper are to conduct: 1) a systematic review of the effects of mastication on sustained attention, and 2) a meta-analysis of the effects of mastication on the performance of participants undertaking cognitive tests. Papers were obtained from MEDLINE and PsycInfo using a systematic approach incorporating defined inclusion and exclusion criteria. Twenty-one papers linking mastication and sustained attention were reviewed. Meta-analysis detected a weak, but statistically significant, improvement in levels of sustained attention when chewing with low between-study heterogeneity (mean Cohen's d = -0.1479 standard deviations, 95% CI [-0.2913, -0.0045], p = 0.043 & I = 0.00%), and a tendency for feelings of alertness to decrease less during cognitive demanding tasks when chewing (mean Cohen's d = 0.3797 standard deviations, 95% CI [-0.0053, 0.7647], p = 0.052 &I = 70.94%). To better understand the effects of mastication on sustained attention and alertness, further research is required which refines existing protocols, eliminates confounding effects such as gum formulation and constituents, and investigates the effects of contiguity, rate, and intensity of chewing.