Obesity Doubles Risk for Incontinence in Younger Women

Norra MacReady

September 20, 2018

Obesity almost doubles the risk for urinary incontinence (UI) in young and middle-aged women compared with women of normal weight, the authors of a new meta-analysis warn.

These findings are significant because those with a history of even mild UI when young are more likely than women without such a history to have increasingly bothersome symptoms as they grow older, and the longer they have the excess weight, the greater the risk for UI, lead author Tayla Lamerton, a PhD candidate in women's health at the University of Queensland, Brisbane, Australia, and colleagues write.

The study was published online September 19 in Obesity Reviews.

Once considered a condition of mostly older or multiparous women, UI, defined as the involuntary loss of urine, has become increasingly prevalent in younger and nulliparous women, leading to a search for causes, Lamerton and colleagues explain. Recent research suggests that overweight and obesity may increase the risk for UI in women, possibly because excess abdominal weight places increased pressure on the bladder, which may, in turn, exceed urethral closure pressure leading to urine leakage.

They suggest that clinicians "emphasize the role of excess weight on pelvic floor weakening and subsequent risk for incontinence" along with its metabolic risks. In fact, maintenance of a healthy weight could be presented to younger women as a strategy for preventing UI.

The data support a new clinical guideline from the US Women's Preventive Services Initiative that recommends all women, even adolescents, be screened for UI once a year, although not all experts agree with this recommendation.

Excess Weight Overshadows Age as a Risk Factor for UI

In their study, Lamerton and coauthors searched for articles published in English up until September 2017. Inclusion parameters were cohorts with a mean age of 55 years or younger at baseline; excess weight measured using body mass index (BMI), weight, or waist circumference; follow-up of more than 2 years; and use of a risk ratio (RR) estimate of the association between excess weight and UI, among other criteria.

The final analysis included 14 studies with 47,293 women from eight countries: Australia, France, United States, Denmark, England, Scotland, Wales, and the Netherlands. Most participants came from a single study with a sample size of 30,982.

Among women who were overweight, defined as a BMI of 25 to 30 kg/m2, the risk for UI was increased by about a third compared with women with a normal BMI (pooled risk estimate, 1.35; 95% CI, 1.20 - 1.53). For women who were obese, defined as a BMI > 30 kg/m2, the pooled risk estimate was 1.95 (95% CI, 1.58 - 2.42), again compared with normal-weight women.

"Overall," the authors write, "the pooled estimate of the risk for developing UI because of excess weight exposure (overweight plus obesity) was 1.68 (95% CI, 1.47 - 1.92)."

They did not observe any differences in UI risk between women younger than 36 years of age and those aged 36 to 53 years.

"This result points to the importance of excess weight, above and beyond age-related risk," they add.

The authors also determined whether excess weight was associated with an increased risk for any of the four subtypes of UI:

  • Stress UI: Involuntary loss of urine associated with activities such as coughing or sneezing;

  • Urge UI: Urinary leakage associated with or immediately preceded by a feeling of urgency;

  • Mixed UI: A combination of urge and stress UI symptoms; and

  • Severe UI: Urinary leakage of unusually high frequency or amount.

Of the 14 studies included in the analysis, five provided risk estimates according to these subtypes. In a pooled risk estimate, the risk for mixed UI was 2.45, followed by 2.28 for severe UI, 1.90 for urge UI, and 1.83 for stress UI. These differences were not significant.

In an overall estimate that combined all subtypes, "excess weight doubled the risk of developing any UI subtype," with an effect size of 2.0 (95% CI, 1.74 - 2.31).

One major limitation was that only five of the studies adjusted for whether women had ever given birth, meaning the risk estimates may not have been completely independent of parity, the authors write.

Also, none of the studies categorized participants according to subcategories of obesity, so estimation of UI risk according to severity of obesity was not possible. Also, the analysis was limited to studies published in English and conducted in high-income Western nations.

UI is a complex issue, especially among younger women, Lamerton said in a news release about the study.

"Understanding overweight and obesity as a determinant of urinary incontinence could play a role in the way we counsel those affected by the condition, and our findings provide a building block to further explore lifestyle interventions for preventing and managing incontinence," she stressed.

The authors have reported no relevant financial relationships.

Obesity Reviews. Published online September 19, 2018. Abstract

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