Urinary incontinence (UI) is both bothersome and common among older men, but few modifiable risk factors have been identified. Among women and younger men, lower body mass index (BMI) is associated with decreased risk of UI. However, lower body mass may have different implications for older men due to age-related changes in body composition and strength. We previously demonstrated that older men with higher BMI and fat mass as well as lower grip and quadriceps strength are more likely to report prevalent UI. We subsequently conducted the first prospective study to test our hypothesis that older continent men with higher adiposity and lower strength would have increased odds of incident UI after 3 years.

The Health, Aging, and Body Composition Study is a prospective, multicenter study of community-dwelling, black and white men and women, aged 70 to 79 years in the United States. Participants were recruited from a random sample of Medicare beneficiaries in 1997, with enhanced community recruitment of black individuals in Pittsburgh, Pennsylvania and Memphis, Tennessee. Cohort exclusion criteria included initial difficulty with activities of daily living, difficulty with walking 1/4 of a mile or climbing 10 steps, recent treatment for cancer, participation in a clinical trial, or intention to relocate from the study areas within 3 years. Our study population included men who had complete data on BMI and UI, were continent at baseline, and had no history of Parkinson’s disease, stroke, prostate or bladder cancer. UI was assessed using structured, interviewer-administered questionnaires at baseline and after 3 years of follow-up. Participants were asked whether they had leaked urine anytime in the past 12 months and if so, at what frequency (<1/month; ≥1/ month; ≥1/week; every day; don’t know). Incident UI was defined by report of urine leakage at least monthly on the follow-up questionnaire. UI subtypes (urgency UI, stress UI, and mixed UI) were identified by asking men when urine leakage usually occurred. Adiposity was assessed via physical examination (BMI and waist circumference) and dual-energy X-ray absorptiometry (fat mass). Upper and lower extremity strength was measured using isokinetic (quadriceps strength) and isometric (grip strength) dynamometers. We used multivariate logistic regression models to evaluate the association between baseline adiposity and strength measures and incident UI among men who reported less than monthly or no UI at baseline. Fully adjusted models included age, race, diabetes mellitus, and self-reported general health status. Assuming the cumulative 3-year incidence of UI is 20% among older men with BMI <25kg/m2 and applying the known BMI distribution in our study population, we had 80% power to detect an odds ratio of 1.8 comparing men with BMI <25kg/m2 to men with BMI ≥30kg/m2.

Of the 1,491 men in the cohort, 822 (55%) men were included in analyses after excluding 258 (17%) with prevalent UI at baseline, 176 (13%) with a history of neurologic disease or genitourinary cancer, 147 (10%) missing UI questionnaire data, and 71 (5%) who died. Baseline demographic and health-related characteristics of the final analytic sample are reported in Table 1. After 3 years of follow-up, 72 (9%) men who were continent at baseline reported incident UI at least weekly and 134 (16%) reported incident UI at least monthly. Urgency UI (60%) and mixed UI (35%) were the most common subtypes, whereas stress UI was rare (5%). In fully adjusted models, associations of adiposity and strength measures with incident UI did not reach statistical significance thresholds (P >0.05 for all; Table 2), although confidence intervals were wide.

In this diverse multicenter, prospective cohort study, we did not observe statistically significant associations between adiposity or strength measures and incident UI among older men after 3 years of follow-up. However, the effect estimates for BMI were similar to prior cross-sectional studies[1] and the confidence intervals included clinically meaningful effects. Contrary to prior studies, waist circumference (as a proxy for central adiposity) and total fat mass did not appear associated with incident UI after adjusting for BMI. Although studies with larger sample sizes are needed to confirm these findings, alternative mechanisms of the previously reported relationship between obesity and UI include regional adiposity, pelvic floor muscle and nerve dysfunction, and systemic metabolic and inflammatory changes.[2] While older men with decreased strength may also have mobility impairments that impair normal voiding[3], our study does not provide evidence to support an association between upper or lower extremity strength and incident UI in older men.

This novel study provides preliminary evidence for the relationship between adiposity, strength, and incident UI in older men. While we did not observe statistically significant associations between adiposity or strength measures and incident UI, our power may have been insufficient to detect modest but clinically meaningful effects. These relationships should be evaluated in larger prospective cohort studies of older men.

Goode, P.S., et al., Population based study of incidence and predictors of urinary incontinence in black and white older adults. J Urol, 2008. 179(4): p. 1449-53.
Subak, L.L., H.E. Richter, and S. Hunskaar, Obesity and urinary incontinence: epidemiology and clinical research update. J Urol, 2009. 182(6 Suppl): p. S2-7.
Suskind, A.M., Frailty and Lower Urinary Tract Symptoms. Curr Urol Rep, 2017. 18(9): p. 67.