The effect of age on lower urinary tract function: a study in women.

Objectives: To identify age-associated changes in female lower urinary tract function across a wide age spectrum, controlling for detrusor overactivity (DO).
Design: Secondary analysis of a cross-sectional study of DO and aging. Eligible volunteers were stratified by age group and presence of DO.
Setting: Community-based volunteers, evaluated in research laboratory.
Participants: Eighty-five ambulatory, nondemented, community-dwelling female volunteers, with and without bladder symptoms suggestive of DO, recruited by advertising, mean age 54 (range 22-90); 75% Caucasian, 21% African American.
Measurements: Comprehensive assessment included bladder diary, uroflowmetry, and detailed videourodynamics. Predefined urodynamic and diary variables were examined for association with age and DO. Mean values of these variables were calculated for subgroups aged 20 to 39, 40 to 59, and 60 and older (14 subjects > or =70).
Results: Maximum urethral closure pressure, detrusor contraction strength, and urine flow rate declined significantly with age (P<.001, P<.001, P=.006, respectively), regardless of whether DO was present. Most elderly individuals continued to empty their bladder almost completely, with normal voiding frequency. Mean number of nocturnal voids was less than one in all age groups. Bladder capacity did not decrease with age (mean 522 mL in oldest group) but was smaller in subjects with DO. Bladder sensation diminished significantly with age (P<.001) but was stronger in subjects with DO.
Conclusion: Female bladder and urethral function appear to deteriorate throughout adult life, whether DO is present or not. Specifically, detrusor contractility, bladder sensation, and urethral pressure decline. The common belief that bladder capacity shrinks with age may be related to DO rather than to aging itself.