A novel method for assessing oral mixing ability based on the spatial clusters quantified by variogram.

BACKGROUND: The two-colour chewing test (TCCT) has been widely used for assessing oral mixing ability, a critical component of masticatory performance. Most studies focused on quantifying the evenness of colour distribution. It remained unknown if the variation of colour clustering was a valid index of oral mixing ability. OBJECTIVE: The study aims to investigate the oral mixing ability based on the spatial clusters quantified by variogram. METHODS: Fifty older people (15 male/35 female, age: 66.0 ± 7.8 years) were assessed for the TCCT and the colour-changeable chewing gum test (CCGT). For the CCGT, we quantified the degree of colour change (ΔE). For the TCCT, the highest peak in colour histogram (HP), the standard deviation of colour values (SDC) and the range of variogram from colour spatial distribution (VARG) were quantified. The participants were grouped according to the contacts of posterior teeth, as assessed by Eichner Index (EI). RESULTS: Highest peak, SDC and VARG showed statistically significant differences between the EI groups (two-tailed independent t test P < .05). Higher VARG (ie a lower degree of clustering) was significantly negatively correlated with ΔE (r = -.36, one-tailed P < .01). The binary logistic regression revealed that among the spatial indices (HP, SDC and VARG), only VARG achieved statistical significance in prediction to the EI group. Eliminating other indices was insignificant to the model performance. CONCLUSIONS: Our results show that the averaged cluster sizes, quantified by variogram, are a valid index for quantifying the TCCT. Compared with other spatial indices, it had the best predictability to the condition of posterior contact.

Brain signatures associated with swallowing efficiency in older people.

Swallowing is a complex movement consisting of the sequential and orderly activation of the swallowing muscles. Neuroimaging evidence has revealed a complex cortical and subcortical representation of voluntary swallowing. The repetitive saliva swallowing test (RSST) is a convenient and simple method for assessing swallowing performance in older people. It remains unclear whether individual differences in swallowing performance are associated with variations in structural brain signatures. We aimed to investigate the association between swallowing efficiency (SWE, measured by the RSST) and gray matter volume (GMV) in healthy older adults. Forty healthy older adults (52-82 years old, 28 female) underwent T1-weighted magnetic resonance imaging (MRI) and clinical assessments of SWE, stimulated/unstimulated salivary flow rate, masticatory cycle, and walking speed. GMV was quantified using a voxel-based morphometry (VBM) approach based on the MRI data. SWE was significantly negatively correlated with age. The association between SWE and hand grip strength, but not the other clinical metrics, was statistically significant. The GMV of the left posterior cerebellum (from cerebellum crus to lobule VIII) was significantly positively correlated with SWE, as evidenced by the results of whole-brain and cerebellum-specific VBM analyses. SWE was significantly positively correlated with the cerebellar volume in the region-of-interest analyses based on automated segmentation. In healthy older adults, swallowing efficiency was positively correlated with cerebellar GMV. The findings suggested that in older people, structural variations of the brain may play a key role in individual differences in swallowing performance.