The 338 randomized women had mean (±standard deviation) age of 53±11 years, baseline BMI of 36±6, weight of 92 (±18) kg, and 24 (±18) urinary episodes per week (10 stress and 14 urge episodes/week). Seventy-seven percent of the women were white, 19% were African American, and 4% reported other ethnic or racial groups. The 6-, 12-, and 18-month assessments, including weight and the 7-day voiding diary, were completed by 304 (90%), 294 (87%), and 287 (85%) of all participants. There were no significant differences between those who attended these assessments and those who did not on baseline demographic characteristics, BMI, or urinary incontinence frequency.
Participants were grouped into their category of weight loss at 6, 12, or 18 months without regard to randomized treatment assignment. The categories were gained weight, lost 0 to less than 5%, lost 5 to less than 10%, or lost 10% or greater of baseline body weight. Participants in the gained weight category gained on average 2.1 (±1.9) kg, 2.8 (±3.1) kg, and 3.5 (±3.2) kg at 6, 12, and 18 months, respectively. shows the number and proportion of women in each of these categories at each time period. As expected, women in the weight loss intervention were overrepresented in the higher weight loss categories at 6, 12, and 18 months (all P<.001). Women in the various weight loss categories did not differ significantly from each other on baseline characteristics, including BMI and urinary incontinence measures ().
Women in Each Weight Loss Category by Visit
Baseline Characteristics According to Magnitude of Weight Loss at 6 Months
Among women who gained weight, lost 0 to less than 5%, lost 5% to less than 10%, and lost at least 10% at 6 months, 18.5%, 12.4%, 5.5%, and 9.5%, respectively, dropped out by 18 months. Participants who dropped out of the study had a greater number of incontinence episodes at baseline (P=.03) and were less likely to be married (P=.02).
We tested the interaction between randomization group and magnitude of weight loss and found that the effect of specific magnitudes of weight loss on urinary incontinence did not differ for women in the weight loss compared with the control group (Pvalues range from .12 to .93). Thus, the weight loss and control group were combined for all subsequent analyses.
shows the adjusted changes in urinary incontinence in each of the weight loss categories. As shown, there was a strong association between magnitude of weight loss and absolute percent reductions in weekly frequency of total, stress, and urge urinary incontinence at 6, 12, and 18 months such that greater weight losses were associated with greater reductions in incontinent episodes frequency. There were no significant interactions between baseline BMI (BMI of less than 35 compared with more than 35) or baseline frequency of urinary incontinence and the weight change categories for any of the measures of urinary incontinence; thus, the relationship between weight change category and improvements in urinary incontinence was not modified by initial BMI or initial severity of incontinence. Similarly, women in the various weight loss categories did not differ in their reported use of the strategies described in the incontinence booklet.
Adjusted Percent Change in Weekly Urinary Incontinence Episode Frequency and Urine Loss According to Magnitude of Weight Loss*
shows the cumulative percentage of women who experienced 0% to 100% reductions in total urinary incontinence episodes at 6, 12, and 18 months, respectively, within each of the weight change categories. At 6 months, the proportion of women who achieved any given degree of improvement in urinary incontinence was lowest in the gained weight category followed by those who lost 0% to less than 5% and highest in those who lost 5% to less than 10% or 10% or greater. There was no further improvement for those who lost 10% or greater compared with those who lost 5 to less than 10% (P=.47). An identical pattern was seen at 12 months (P=.78); however, at 18 months, the gained weight category differed from all three of the weight loss categories with no difference between those who lost 0% to less than 5%, 5% to less than 10%, or 10% or greater (pairwise comparison P values from log-rank test ranged from .47 to .85).
Cumulative proportion of participants in each weight change category who experienced 0–100% reductions in total urinary incontinent episodes at 6 months (A), 12 months (B), and 18 months (C).
As noted, we selected a 70% reduction in total, stress, or urge incontinent episodes per week as a clinically significant threshold. shows the number and percentage of women in each weight loss category who achieved or failed to achieve this threshold. Using those who gained weight as the reference, we found () that the adjusted odds of achieving at least a 70% reduction in total, stress, or urge incontinent episodes per week was significantly increased by greater weight losses (with the exception of stress incontinence at 6 months). Again, we found a strong association between weight losses of 5% to less than 10% of body weight and urinary incontinence improvement without further benefit among women with 10% or greater weight loss (P>.20 for all outcomes at 6, 12, and 18 months). Women who lost 5% to less than 10% of their body weight had 3.7 times the odds of achieving a 70% or greater reduction in total incontinent episodes compared with women who gained weight at 12 months and 2.4 times the odds at 18 months.
Observed Number and Percent of Women With 70% Reduction in Number of Incontinent Episodes per Week Reported in Voiding Diary
Adjusted Odds of at Least 70% Reduction in Number of Incontinent Episodes per Week Reported in Voiding Diary by Type of Incontinence and Magnitude of Weight Loss Compared With Weight Gain (Reference Group)*
Satisfaction with urinary incontinence outcomes was also strongly associated with amount of weight loss At 6 months, the percent of participants who reported being moderately or very satisfied with overall changes in leakage was 37%, 64%, 75%, and 80% for participants who gained weight and those losing 0% to less than 5%, 5% to less than 10%, or 10% or greater, respectively (P<.001). The percentages at 12 months were 49%, 62%, 78%, and 81% (P<.001), respectively, and 54%, 63%, 74%, and 79% at 18 months (P=.01).