The effects of age and childbirth on anal sphincter function and morphology in 999 symptomatic female patients with...

Conflicting data exist on the contributions of advancing age and childbirth on the structure and function of the anal sphincter. This study aimed to examine the relative contributions of age and childbirth in a large cohort of women referred for investigation of symptoms of colorectal dysfunction (fecal incontinence and constipation).

This study was conducted at a specialist surgical colorectal investigation unit in a university teaching hospital.

Retrospective analysis was performed on prospectively collected demographic, symptom profile, and physiologic data from 3686 female patients. Strict exclusion criteria were applied, leaving 999 patients for univariate, multivariate, and logistic statistical modeling.

The effects of independent variables alone and in combination on anal sphincter pressures (resting and squeeze increment) and the presence of sphincter defects (internal and external) were expressed as regression coefficients and odds ratios.

Median age was 42 years (range, 16-88), and parity was 2 (range, 0-11); 16% were nulliparous. Three hundred sixty patients had fecal incontinence, 352 had constipation, and 287 had combined symptoms. Anal resting tone decreased with age by 0.66 cm H2O per year, and by 4.3 cm H2O per birth, and was associated with both internal and external anal sphincter defects (p = 0.0001 for both). Squeeze increment pressures decreased by 0.3 cm H2O per year, and by 3.8 cm H2O per birth; decreased pressures were, however, only significantly associated with external anal sphincter defects (p = 0.0001) as a result of childbirth. Cesarean delivery was protective against both reduced anal pressures and sphincter defects. Pudendal nerve terminal motor latencies increased bilaterally with age and with vaginal delivery; the impact of both was greater on the left nerve. Rectal sensation was unaffected by age or parity.

Aging predominantly affects anal resting pressures; childbirth, particularly instrumental delivery, is detrimental to the structure and function of the external sphincter.