Age, parity, and prolapse: interaction and influence on levator bowl volume.

INTRODUCTION AND HYPOTHESIS

The objective was to test the hypotheses that a linear relationship exists between age and levator bowl volume (LBV); and that age, parity, and prolapse are independently associated with LBV.

METHODS

We conducted a secondary analysis of data from nulliparous women, parous controls, and prolapse (Pelvic Organ Prolapse Quantification (POP-Q) Ba ≥ 1 cm) cases from each of three age groups: young (≤40), mid-age (50-60), and older (≥70). LBV was measured using MRI at rest and Valsalva as the 3D space contained above the levator ani muscles and below the sacrococcygeal junction-to-inferior pubic point reference plane. Linear regression models were used to examine the effects of age, parity, prolapse, and their interactions (ageparity and ageprolapse) on LBV.

RESULTS

Each group consisted of 9-12 women. LBV increased with age in a nonlinear fashion. For nulliparous women, the median value increased 4.7% per decade from the young to mid-age group and 84% per decade from the mid-age to older group; for parous controls, the corresponding increases were 38% and -0.5%; and for women with prolapse, they were 46% and 11%. Age and prolapse status (both p<0.001) were found to be significant independent predictors of LBV. Interactions between ageprolapse (p=0.003) and ageparity (p=0.045) were also independently associated with LBV.

CONCLUSIONS

Parity and prolapse influence how age affects LBV. In nulliparous women, age had little effect on LBV until after mid-age. For women with prolapse, LBV increased at a much earlier age, with the biggest difference occurring between young and mid-age women.