Effects of Age and Sex on the Anorectal Sensory Threshold to Electrical Stimulation: A Single-center Observational Study

OBJECTIVES: Anorectal sensation is an essential component for maintaining normal defecation and continence. This study aimed to investigate changes in anorectal sensation with age and sex using the anorectal sensory threshold to electrical stimulation in a large population with a broad age spectrum. METHODS: This study enrolled consecutive adult patients (20-89 years old) who underwent anorectal physiology tests to screen for functional or organic anorectal disease. Anorectal sensitivity was measured using an endoanal electrode with a 45-mm long bipolar needle. A constant electrical current was delivered to the lower end of the rectum and the anal canal. The minimum current in milliamperes at which the initial sensation was felt was defined as the sensory threshold. RESULTS: Overall, 888 patients were included in this study. The most frequent comorbidities were constipation and hemorrhoids. The median sensory threshold for all patients was 0.5 (interquartile range, 0.2-1.5) mA, and the overall sensory threshold was significantly higher in men than in women. The 95% confidence interval of the sensory threshold for men and women were 0.1-6.8 and 0.1-5.1 mA, respectively. The sensory threshold increased significantly with age in both sexes (men, r = 0.384; women, r = 0.410). There was no sex difference in the sensory threshold between ages 20 and 40 years; however, between ages 50 and 70 years, men had a higher sensory threshold than women. CONCLUSIONS: The anorectal sensory threshold to electrical stimulation increased with age, and the influence of aging was more significant in men than in women.