Pilot kinematic study of swallowing in healthy adults: age-related, individualised, and lateralised patterns of bolus trajectories.

Background: Swallowing function may undergo subtle changes with age, even in asymptomatic adults. However, objective and reproducible metrics for characterising normal swallowing motion remain limited.

Aims/objectives: This pilot study aimed to quantify the spatiotemporal trajectory of the bolus centre of mass (CoM) during swallowing in healthy adults and explore its potential as a kinematic marker for identifying individualised and age-associated patterns.

Materials and methods: Thirteen healthy adults (aged 26-62 years) underwent videofluoroscopic swallowing studies using contrast-enhanced liquid boluses. Bolus CoMs were tracked throughout the oropharyngeal phase. Multiple swallows per participant were analysed to assess intra-individual consistency. K-means clustering and silhouette analysis were applied to the CoM trajectory data to evaluate pattern reproducibility and explore potential age-related differences.

Results: CoM trajectories were highly consistent within individuals (silhouette score = 0.718). Clustering revealed age-related patterns: older participants exhibited more centralised trajectories, whereas younger participants demonstrated more lateralised movement. Additional differences in bolus descent and pharyngeal coordination existed between age groups.

Conclusions and significance: Bolus CoM trajectory analysis is a feasible and reproducible approach for assessing swallowing kinematics. These trajectories may represent individualised motor signatures and could help identify subtle, age-related changes. The findings underscore the need for personalised dysphagia assessment and rehabilitation strategies.