Effect of chewing or compressing food on autonomic nervous activity in older adults.

OBJECTIVE: To determine if autonomic nervous activity increases in older people during mastication and how this activity is related to the softness of food. We hypothesised that the coefficient of variation of R-R intervals (CVRR), high-frequency (HF) power, low-frequency (LF) power, LF/HF ratio and total power increase during chewing foods within the range of softness from moderate food to extremely soft food in older adults.

MATERIALS AND METHODS: Participants were 20 older volunteers (71-90 year old). CVRR and HF on the electrocardiogram (ECG) were used as indices of parasympathetic nervous activity. LF and the LF/HF ratio on the ECG were used as indices of sympathetic nervous activity. Total power, reflecting the level of autonomic nervous activity, was also measured. Participants were asked to chew gum with three different degrees of softness, or to compress extremely soft gum between their palate and tongue.

RESULTS: There were significant differences in HF between at resting and all chewing/compressing conditions, but no significant differences relating to food softness. There were significant differences in total power between at resting and all chewing/compressing conditions, but no significant differences relating to food softness. There were no significant differences in LF, LF/HF and CVRR among all conditions.

CONCLUSION: Autonomic nervous activity, especially parasympathetic activity in older adults, increased during chewing and compressing food when compared to activity while at rest. Within the range of food's softness from moderate to extreme soft, food's softness had no measurable effect on autonomic nervous activity.