title: High familial risk of atrial fibrillation/atrial flutter in multiplex families: a nationwide family study in Sweden.
abstract: BACKGROUND
  Although the heritability of atrial fibrillation/atrial flutter (AF/AFl) has been determined, the familial risk in multiplex families is unclear. The main aim of this nationwide study was to determine the familial risk of AF/AFl in multiplex families.
  
  
  RESULTS
  We examined the familial risk of AF/AFl in the entire Swedish population. We linked Multigeneration Register data on individuals aged 0 to 76 years with Hospital Discharge Register data for 1987-2008 and Outpatient Register data for 2001-2008 to compare AF/AFl risk among relatives of all 300 586 individuals with AF/AFl with that among relatives of unaffected individuals. We used conditional logistic regression to investigate differences in exposure between cases and controls. Parents (odds ratio [OR] 1.95 [95% CI 1.89 to 2.00]) and siblings (OR=3.08 [3.00 to 3.16]) of cases had higher odds of AF/AFl than did parents and siblings of controls. AF/AFl ORs were increased in both sexes. For 2% of cases, both parents had AF/AFl, compared with only 0.7% of controls (OR=3.60 [3.30 to 3.92]). Moreover, 3% of cases had ≥2 siblings with AF/AFl, compared with 1% of controls (OR=5.72 [5.28 to 6.19]). In premature cases (diagnosed at age <50 years), the ORs were 5.04 (4.36 to 5.82) and 8.51 (6.49 to 11.15) for AF/AFl in both parents and AF/AFl in ≥2 siblings, respectively. The overall spouse OR was 1.16 (1.13 to 1.19).
  
  
  CONCLUSIONS
  Family history of AF/AFl increases the odds of AF/AFl in first-degree relatives. High familial risks were observed in multiplex families.
authors.affiliation: Center for Primary Health Care Research, Region Skåne/Lund University, Malmö, Sweden. bengt.zoller@med.lu.se
authors.forename: Bengt
authors.initials: B
authors.lastname: Zöller
authors.forename: Henrik
authors.initials: H
authors.lastname: Ohlsson
authors.forename: Jan
authors.initials: J
authors.lastname: Sundquist
authors.forename: Kristina
authors.initials: K
authors.lastname: Sundquist
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D001282:Atrial Flutter / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005190:Family; D005220:Fathers; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D040941:Heredity; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008019:Life Style; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009035:Mothers; D016017:Odds Ratio; D010375:Pedigree; D010641:Phenotype; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D035781:Siblings; D018454:Spouses; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult