Variations in oral performance and processing behaviours among older adults: Associations with gastric emptying, postprandial glucose and insulin responses

Older adults often experience deterioration in oral health and oral-related abilities, with tooth loss, impaired masticatory performance, alterations to salivary flow and composition all being common. Additionally, other ageing-related physiological changes happen, including delayed gastric emptying and higher postprandial glycemic responses. The interaction between oral-related factors and metabolic responses has been researched in younger adults, but not in older age groups. This study aimed to explore oral performance measures (OPMs) and oral processing behaviours (OPBs) and their associations with gastric emptying (GE) and postprandial glucose and insulin responses in adults aged ≥65 years. Participants attended one visit after an overnight fast and were provided with a fixed-portion breakfast, which they were asked to consume in full. Eating behaviours were coded to quantify OPBs (including chewing and eating rate). OPMs (salivary flow rate, salivary alpha-amylase, bolus saliva uptake and masticatory performance) and questionnaire data were collected. Over three postprandial hours, GE was measured using labelled breath samples, and glucose and insulin responses were measured in capillary blood samples. Increased bolus salivary uptake was associated with greater masticatory performance, greater stimulated salivary flow rate and a slower eating rate. Greater masticatory performance was related to faster GE times. Faster eating rates and reduced chewing were associated with lower early postprandial glucose responses (up to peak glucose (45 min)); however, they were not associated with postprandial insulin responses or GE. This research highlights the significant, complex associations between oral performance, oral processing behaviours and postprandial metabolism in older adults.