Influence of smoking, coffee, and tea consumption on bladder pain syndrome in female twins.

OBJECTIVES To assess the influence of smoking, coffee and tea consumption on the risk for bladder pain syndrome (BPS) using the O'Leary Interstitial Cystitis Symptom Index (ICSI). METHODS In 2005, all twins born between 1959 and 1985 in Sweden (n = 42,852) were invited to participate in a web-based survey to screen for complex diseases, including BPS. Analyses were limited to female twins with information regarding bladder pain symptoms (n = 9349). Women with an ICSI score ≥6 with required nocturia and bladder pain were defined as having BPS symptoms. Logistic regression was used to estimate odds ratios (ORs) with 95% confidence intervals (CIs). Environmental and genetic influences were assessed in co-twin control analysis. RESULTS Tea consumption was associated with an increased risk for BPS (OR 1.26, 95% CI 1.02-1.55 for low tea consumption; OR 1.74, 95% CI 1.24-2.44 for high tea consumption). Coffee consumption was not a risk factor for BPS (OR 1.1, 95% CI .84-1.45). Former and current smoking was associated with a higher risk of BPS (OR 1.5, 95% CI 1.18-1.89; and OR 1.49, 95% CI 1.16-1.92, respectively), but results from co-twin control analysis suggested that the association between smoking and BPS was confounded by familial factors. CONCLUSIONS Tea and smoking are environmental risk factors for BPS, which are amenable to intervention. The effects of smoking on the risk for BPS may, however, be confounded by familial factors.