Table 4.

Twin similarity and concordance rates for lower urinary tract symptoms in female twins grouped by zygosity^*

	Monozygotic female twins n = 1392				Dizygotic female twins n = 883
	Concordant pairs	Discordant pairs	Probandwise concordance rate1	Tetrachoric correlations2 (95% CI)	Concordant pairs	Discordant pairs	Probandwise concordance rate1	Tetrachoric correlations2 (95% CI)	p value3
Micturition frequency (ICS)	101	329	0.38	0.42 (0.33–0.51)	32	129	0.33	0.13 (−0.01–0.27)	0.34
≥8 micturitions/24 h	154	406	0.43	0.40 (0.32–0.48)	53	306	0.26	0.06 (−0.06–0.19)	<0.0001
Nocturia (ICS)	643	482	0.73	0.40 (0.32–0.47)	346	399	0.63	0.07 (−0.04–0.18)	<0.0001
Nocturia ≥2 micturitions/night	137	364	0.43	0.44 (0.35–0.52)	59	253	0.32	0.25 (0.13–0.37)	0.005
Overactive bladder without incontinence	19	179	0.18	0.28 (0.13–0.43)	8	109	0.13	0.18 (−0.03–0.40)	0.38
Overactive bladder with incontinence	4	53	0.13	0.41 (0.16–0.66)	3	31	0.16	0.48 (0.19–0.78)	0.76
All overactive bladder	30	218	0.22	0.30 (0.17–0.43)	13	136	0.16	0.20 (0.01–0.38)	0.28
Stress urinary incontinence	20	102	0.28	0.56 (0.42–0.70)	12	89	0.21	0.40 (0.21–0.59)	0.33
Urge urinary incontinence	7	66	0.18	0.47 (0.27–0.68)	3	57	0.10	0.24 (−0.05–0.54)	0.30
Mixed urinary incontinence	4	51	0.14	0.45 (0.19–0.70)	2	40	0.09	0.29 (−0.05–0.63)	0.60
All urinary incontinence	28	121	0.32	0.57 (0.45–0.69)	14	111	0.20	0.33 (0.15–0.51)	0.07

ICS = International Continence Society; CI = confidence interval.

^*Higher concordance rates or tetrachoric correlations among monozygotic than dizygotic twins indicates genetic effects.

¹Probandwise concordance rate is a measure of twin similarity, which is independent of prevalence.

²Tetrachoric correlations, r, indicate the upper limit of the genetic variance component.

³The p value for test of homogeneity of probandwise concordance rates between monozygotic and dizygotic pairs.