The aging lower urinary tract: a comparative urodynamic study of men and women

The fact that aging women report similar voiding symptoms as age-matched men prompted us to compare age-related changes of urodynamic parameters in both sexes.

Four hundred thirty-six patients (253 men and 183 women) 40 years of age or older underwent the following investigations: free uroflowmetry, measurement of postvoid residual volume, and full urodynamic testing, including a pressure-flow study (pQs). Additional investigations were a urethral pressure profile in women and quantification of prostate volume by transrectal ultrasonography in men. All men were referred for lower urinary tract symptoms suspicious of bladder outflow obstruction and women predominantly for urinary incontinence. Patients with previous surgery of the lower urinary tract (prostate, bladder, urethra) and those taking medication with a major effect on voiding function (alpha-receptor blockers, 5 alpha-reductase inhibitors, anticholinergic agents) were excluded.

The mean +/- standard deviation (SD) age in the female (f) population (n = 183) was 59 +/- 16 years (range 40 to 93), in the male population (m) (n = 253) 67 +/- 9 years (range 40 to 90). In both sexes, we observed a statistically significant increase of postvoid residual volume (f: P = 0.0001; m: P = 0.02) and a decrease of peak flow rate (f: P = 0.019; m: P = 0.014), average flow rate (f: P = 0.007; m: P = 0.04), voided volume (f: P = 0.007; m: P = 0.002), and bladder capacity determined by urodynamics (f: P = 0.003; m: P = 0.0004) with progressing age. In both sexes, there were no age-related changes (P >0.05), demonstrable for maximum detrusor pressure and detrusor pressure at peak flow rate. In women, there was a significant decrease of functional urethral length (P = 0.012) and maximum urethral closing pressure (P = 0.0001) with higher age; in men, the prostate volume increased significantly with age (P = 0.0001). With respect to detrusor instability, we observed an increase in men from 23.4% (40 to 60 years) to 46.7% (more than 80 years) (P = 0.004), whereas in women no significant age-related changes were present (P >0.05).

These data show that age-associated urodynamic changes in both sexes are comparable for a number of parameters. They provide an explanation for the fact that aging women report comparable voiding symptoms as men and suggest a primary, non-sex-specific aging process of the urinary bladder.