Age-related changes in oro-facial motor performance
Older adults speak 20-30% slower than younger adults. A decline in articulatory speed capacity has often been suggested; however, direct investigations on speech motor performance have rarely been conducted. Therefore, this study sought to determine if jaw speed capacity is reduced in older adults. This study included 36 female participants in four age groups: young adult, middle-aged, young-old, and very old. Each participant completed a jaw oscillation task at seven metronome paces. Similar to previous studies on upper limb speed capacity, participants were asked to tap a fixed target with their jaw at each metronome beat. The metronome pace determined the jaw movement duration and the target determined the jaw movement excursions during the experimental conditions. Jaw peak speeds, excursion, and movement durations during the jaw closing strokes were compared between the four age groups. Study outcomes showed that jaw speed capacity was significantly lower in the youngest age group relative to all other age groups. Jaw speed capacity did not significantly differ between middle-aged, young-old, and very old adults. These findings contrasted previous reports of aging studies on limb speed capacity. Further, these findings on jaw speed capacity suggested that jaw peak speed may not be a factor that contributes to a slowed speaking rate in older adults. In the future, jaw speed capacity of male speakers needs to be investigated. Further, aging-related changes in tongue and lip speed capacities also should be determined to gain more comprehensive insights in physiologic factors that may affect speaking rates of older adults.