Effect of age, sex and parity on anorectal function.

Ninety-one healthy subjects (51 women; age range 16-85 years) were studied prospectively to determine the effect of age, sex and parity on anorectal function. Maximum resting pressure, voluntary contraction pressure, rectal sensation to distension, rectal and mid-anal electrosensitivity, perineal descent, pudendal nerve terminal motor latency and fibre density of the external and sphincter were measured. Sex influenced mean(s.d.) voluntary contraction pressure (148(56) versus 95(43) cmH2O for men versus women, P < 0.0001), perineal descent on straining (1.0(0.5) versus 1.3(0.4) cm, P = 0.02) and fibre density (1.43(0.14) versus 1.52(0.15), P = 0.02). Age influenced resting pressure (r = -0.43, P = 0.0001), perineal position at rest (r = -0.55, P < or = 0.0001), mid-anal electrosensitivity (r = 0.42, P = 0.0001) and rectal electrosensitivity (r = 0.54, P < 0.0001). Parity affected mean(s.d.) voluntary contraction pressure (105(53) versus 75(20) cmH2O for nulliparous versus parous women, P = 0.04) and mid-anal electrosensitivity (5.3(2.3) versus 4.5(2.3) mA, P = 0.02). Increasing age leads to perineal descent at rest, slowed pudendal nerve conduction, a fall in resting anal pressure and decreased anorectal sensory function. Women have a lower and squeeze pressure, greater perineal descent, longer pudendal nerve terminal motor latency and a greater muscle fibre density than men. Parity leads only to lower squeeze pressure.