Purpose: Bladder pain syndrome/interstitial cystitis is a poorly understood condition that can cause serious disability. We provide the first population based symptom prevalence estimate to our knowledge among United States adult females.

Materials and methods: We developed and validated 2 case definitions to identify bladder pain syndrome/interstitial cystitis symptoms. Beginning in August 2007 we telephoned United States households, seeking adult women with bladder symptoms or a bladder pain syndrome/interstitial cystitis diagnosis. Second stage screening identified those subjects who met case definition criteria. Each completed a 60-minute interview on the severity and impact of bladder symptoms, health care seeking and demographics. Data collection ended in April 2009. Using population and nonresponse weights we calculated prevalence estimates based on definitions spanning a range of sensitivity and specificity. We used United States Census counts to estimate the number of affected women in 2006. The random sample included 146,231 households, of which 131,691 included an adult female. Of these households 32,474 reported an adult female with bladder symptoms or diagnosis, of which 12,752 completed the questionnaire.

Results: Based on the high sensitivity definition 6.53% (95% CI 6.28, 6.79) of women met symptom criteria. Based on the high specificity definition 2.70% (95% CI 2.53, 2.86) of women met the criteria. These percentages translated into 3.3 to 7.9 million United States women 18 years old or older with bladder pain syndrome/interstitial cystitis symptoms. Symptom severity and impact were comparable to those of adult women with established diagnoses. However, only 9.7% of the women reported being assigned a bladder pain syndrome/interstitial cystitis diagnosis.

Conclusions: Bladder pain syndrome/interstitial cystitis symptoms are widespread among United States women and associated with considerable disability. These results suggest bladder pain syndrome/interstitial cystitis may be underdiagnosed.