Overactive bladder (OAB) syndrome remains poorly understood. This study applied a classical twin model to determine the degree of genetic and environmental influences for OAB syndrome; whether the same factors influence both OAB-dry and wet, and each of anxiety, depression, and irritable bowel syndrome (IBS).

5092 subjects from a twin database completed relevant validated questionnaires. Structural equation modelling with Akaike’s information criterion was used, with both univariate and bivariate analyses.

3540 subjects were included. Median age was 64, 83% were female, and 25% reported OAB-wet. 

Univariate models reported heritability of OAB syndrome and OAB-wet to be 41% and 37%. Non-shared environment contributed to 59% of variance for OAB syndrome and 63% for OAB-wet. 

Bivariate heritability between OAB-dry and wet was 57%. Non-shared environmental covariance accounted for 43%. Genetic correlation was 48% and shared environmental correlation was 26%. 

Phenotypic and non-shared environmental covariance between OAB and IBS were 22% and 77% respectively. Genetic and environmental correlation were 9.5% and 44%. 

Phenotypic and non-shared environmental covariance between OAB and anxiety were 19% and 81% respectively. Genetic and environmental correlation were 9% and 42%. 

Phenotypic and non-shared environmental covariance between OAB and depression were <0.01% and 99.9% respectively. Genetic and environmental correlation were <0.01% and 53%.

Heritability of OAB was around 40% with residual differences explained by non-shared environment. Only 48% of genetic and 26% of environmental factors overlap between OAB-dry and wet, suggesting differing pathophysiology. There was little genetic overlap between OAB and IBS, anxiety, and depression.

We found that the heritability of OAB is around 40%, with the rest of the differences between twins with OAB explained by non-shared environment (60%). We found that the genetic overlap between OAB and other common conditions (irritable bowel syndrome, anxiety and depression) was low, suggesting that the diseases are largely unrelated from a genetic perspective.
Understanding the heritability of OAB will help us shape future research to investigate the “other” 60% of causes of OAB, focusing on finding causative factors that can be modified.