AB305. SPR-32 Aging effects on the central motor control of the external anal sphincter in women

OBJECTIVE: Accumulated clinical evidence has shown that aging is associated with deficits in the central nerve system (CNS) that leads to disruption in descending excitation. Whether this is true in pelvic floor muscles remains unclear. This study aimed to study whether there is evidence of an aging-associated decreasing descending excitation to the motoneuron pool of the external anal sphincter (EAS) in women. METHODS: Surface electromyography (EMG) signals of the EAS were acquired from 14 female subjects (38.6±16.6 years, range: 20–73 years, no anorectal disorders) during maximum squeeze using a high-density rectal probe. Motor unit (MU) action potentials were separated using our K-means clustering and convolution kernel compensation algorithm, with the firing rate of each MU obtained. The mean MU firing rate, a key marker to assess the motor control of the CNS, was calculated for all decomposed MUs for each subject. Linear regression analysis was performed to study the impact of aging on the mean MU firing rate. RESULTS: The mean MU firing rate was 7.4±2.1 Hz. Linear regression showed a decreasing, though not significant, trend with advancing age (P=0.10), suggesting a possible deficit in the CNS of aged women in driving the lower motoneurons to activate the EAS. Our ongoing recruitment of more aged women will help us consolidate this observation, to offer valuable insights into the mechanism of aging-associated anorectal disorders. CONCLUSIONS: This study represents the first effort to use advanced high-density surface EMG analysis to noninvasively evaluate aging effects on the central motor control of the EAS in women. FUNDING SOURCE(S): NIH DK082644 and the University of Houston