The researchers enrolled 240 women with bladder muscle overactivity, or overactive bladder syndrome, that had not responded to previous treatment. The women were randomly allocated injections of either Botulinum toxin A (botox) or placebo (saltwater) into the wall of the bladder. Women with another common type of incontinence, stress incontinence, were not included in the study.
The participants kept a diary over three days, recording the number of times they:
emptied their bladder
felt an urgent need to empty their bladder
experienced an unintentional passing of urine (or leakage)
The women also completed a questionnaire that assessed their quality of life, as overactive bladder syndrome often has a significant negative impact on patient quality of life.
The researchers conducted follow-up sessions with the women on average at six weeks, three months and six months after treatment. They assessed differences in the frequency of the above three symptoms between the two treatment groups. They also compared quality of life scores, treatment complications and time until troubling symptoms returned between the two groups.
The researchers used appropriate statistical methods to assess differences in frequency of symptoms between the two groups.