Decrease in stereognostic ability of the tongue with age

Rehabilitation of eating and swallowing functions from the viewpoint of quality of life should attempt to restore not only the physical, but also sensory function. As the size and shape of the intra-oral bolus of food provides oral sensory information important for eating and swallowing, we investigated the stereognostic ability of the tongue in 269 young adults (mean age: 24.5 years) and 60 seniors (mean age: 80.5 years); all of whom had no eating or swallowing complaints. Assessment of the stereognostic ability involved identifying 20 differently shaped test pieces placed in the oral cavity. The young adults identified a significantly higher number of differently shaped test pieces than the seniors (mean correct number of responses: 16.5 and 10.1 respectively; P < 0.001). Gender and the presence of palatal covers did not have any significant effect on stereognostic ability. The test pieces were categorized into six groups based on the shape. When the young adults misidentified a piece, they often selected another piece within the same group, almost never selecting a piece from another group. The seniors, however, chose test pieces from different groups. Moreover, to determine whether stereognosis could be improved through training, we conducted training involving four senior subjects in their 80s, who correctly identified 10 or fewer pieces. After the training, the number of correct answers increased significantly (P < 0.05). These findings indicate that seniors show decreased stereognostic ability of the tongue compared with young adults and suggest the possibility of recovering the ability using our training method.