Association between regional brain volume and masticatory performance differed in cognitively impaired and non-impaired older people.

Older patients with cognitive impairment exhibit worse masticatory performance (MP), which may be attributed to poorer abilities of control, learning, and adaptation of oral sensorimotor functions. This study tested the hypothesis that the association between the structural signature of the right premotor cortex (which relates to sensorimotor integration) and masticatory performance would differ between cognitively impaired (CI) and healthy older people. Thirty-one CI and 31 non-CI older participants (aged 60-84 years; male: female = 28: 34) were recruited and between-group matched for the average age and sex ratio. All the participants received T1-weighted magnetic resonance imaging (MRI) and assessments of MP and the number of missing teeth (NMT). Voxel-based morphometry (VBM) was performed to quantify the gray matter volume (GMV). VBM analyses revealed that in the non-CI but not the CI group, MP was positively correlated with regional GMV at the right premotor cortex (PMC) (p = 0.036, corrected for familywise error under small volume correction), controlling for the participants' sex, age, NMT, and total intracranial volume. Multiple linear regression models revealed that in the non-CI group, the right PMC (beta = 0.3, p = 0.049) was a significant predictor of individual MP. In the CI group, only NMT (beta = -0.7, p = 0.001) was a significant predictor of MP. In non-CI older people, both the NMT and the regional GMV of the right PMC contributed to individual MP. In contrast, in CI patients, tooth loss was the dominant factor in MP. An altered association of the brain-stomatognathic system could be linked to cognitive impairment.