Familial aggregation of atrial fibrillation: a study in Danish twins.
BACKGROUND
Heritability may play a role in nonfamilial atrial fibrillation (AF). We hypothesized that a monozygotic (MZ) twin whose co-twin was diagnosed with AF would have an increased risk of the disease compared with a dizygotic (DZ) twin in the same situation.


RESULTS
A sample of 1137 same-sex twin pairs (356 MZ and 781 DZ pairs) in which one or both members were diagnosed with AF were identified in The Danish Twin Registry. Concordance rates were twice as high for MZ pairs than for DZ pairs regardless of sex (22.0% versus 11.6%, P<0.0001). In a Cox regression of event-free survival times, we compared the time span between occurrences of disease in MZ and DZ twins. The unaffected twin was included when his or her twin-sibling (the index twin) was diagnosed with AF. After adjustment for age at entry, MZ twins had a significantly shorter event-free survival time (hazard ratio, 2.0; 95% CI, 1.3 to 3.0), thereby indicating a genetic component. Using biometric models, we estimated the heritability of AF to be 62% (55% to 68%), due to additive genetics. There were no significant differences across sexes.


CONCLUSIONS
All the analyses of twin similarities in the present study indicate that genetic factors play a substantial role in the risk of AF for both sexes. The recurrence risk for co-twins (12% to 22%) is clinically relevant and suggests that co-twins of AF-affected twins belong to a high-risk group for AF.
Christophersen
Ingrid Elisabeth
IE
The Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Cardiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
Ravn
Lasse Steen
LS
Budtz-Joergensen
Esben
E
Skytthe
Axel
A
Haunsoe
Stig
S
Svendsen
Jesper Hastrup
JH
Christensen
Kaare
K
D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000453:epidemiology* / Q000235:genetics*; D001699:Biometry; D003718:Denmark / Q000453:epidemiology; D005192:Family Health; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008957:Models, Genetic; D015995:Prevalence; D016016:Proportional Hazards Models; D012042:Registries / Q000706:statistics & numerical data; D012307:Risk Factors; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic