Heritability and risk factors of uterine fibroids--the Finnish Twin Cohort study.
OBJECTIVE
Our aim was to study heritability, risk factors and hospitalization for uterine fibroids.


METHODS
A random sample of 80 MZ and 80 DZ twins from the Finnish Twin Cohort were invited and 51% of the eligible women (n=82, 17 MZ and 16 DZ pairs, 40-47 years, mean age 43.0), underwent a transvaginal ultrasound. The entire cohort of 13872 women was linked to the national hospital discharge registry 1972-1990.


RESULTS
Prevalence of fibroids was 66% and the average number of fibroids 1.7. The casewise concordance for being hospitalized for uterine fibroids was higher in MZ (0.31, 95% CI 0.24-0.37) than in DZ pairs (0.18, 95% CI 0.14-0.22). The proportion of variance in liability to fibroid hospitalization accounted for by genetic factors was 54.8% (95% CI 46.2-62.7%). Women with fibroids had higher body mass index (23.7 vs 21.7, P=0.0086), lower age at first birth (25.7 vs 29.3, P=0.012) and higher parity (3+ children 48.2 vs 29.6%, P=0.009) than women without fibroids. Risk ratio (RR) for fibroids in a MZ twin whose sister had been diagnosed with fibroids was 1.1 (95% CI 0.08;15), for a DZ twin 1.1 (95% CI 0.16;8.8) and for all twins 1.3 (95% CI 0.3; 6.1). Intraclass correlation for the number of fibroids was 0.24 for MZ and 0.11 for DZ twins, yielding an heritability estimate of 0.26.


CONCLUSIONS
Reproductive and anthropometric factors may have at least as large role in pathogenesis of fibroids than genetic factors.
Luoto
R
R
Tampere School of Public Health, University of Tampere, Tampere, FIN-33014, Finland. Riitta.Luoto@uta.fi
Kaprio
J
J
Rutanen
E M
EM
Taipale
P
P
Perola
M
M
Koskenvuo
M
M
D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D020022:Genetic Predisposition to Disease; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007889:Leiomyoma / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D008875:Middle Aged; D015995:Prevalence; D012042:Registries; D012307:Risk Factors; D014463:Ultrasonography; D014594:Uterine Neoplasms / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*