title: Familial clustering of myocardial infarction in first-degree relatives: a nationwide study.
abstract: OBJECTIVE
  Family history is an established risk factor for myocardial infarction (MI), but it is not clear how this risk changes with number and gender of first-degree relatives with MI. We used the entire Danish population to examine the importance of MI in siblings and parents.
  
  
  RESULTS
  This study is a retrospective nationwide register-based cohort study including registered relatives to all Danish citizens diagnosed with MI in the period 1978-2010. In the entire Danish population we identified siblings to 7552 patients with a first-time MI. The rate ratios (RR) calculated by Poisson models showed an RR of 4.30 (95% confidence interval 3.53-5.23) for siblings of a patient with MI. Children of parents with MI also showed high risk: for children of a maternal case RR 2.40 (2.20-2.60), and of a paternal case RR 1.98 (1.98-2.09), respectively; P value for gender interaction <0.0001. A paternal case with MI at an age <50 years was associated with an RR of 3.30 (2.92-3.72) while a case >50 years was associated with a risk of 1.83 (1.73-1.93). For maternal cases below and above 50 years of age the risks were 3.23 (2.56-4.10) and 2.31 (2.11-2.52), respectively.
  
  
  CONCLUSIONS
  First-degree relatives of a patient with myocardial infarction themselves have a substantial higher risk of myocardial infarction. The risk is particularly elevated when the MI case is the mother or a sibling, and when the MI case has the infarction before the age of 50 years.
authors.affiliation: Department of Cardiology, Gentofte Hospital, University of Copenhagen, Niels Andersens Vej 65, 2900 Hellerup, Denmark. mia_nielsen7@hotmail.com
authors.forename: Mia
authors.initials: M
authors.lastname: Nielsen
authors.forename: Charlotte
authors.initials: C
authors.lastname: Andersson
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Gerds
authors.forename: Per Kragh
authors.initials: PK
authors.lastname: Andersen
authors.forename: Thomas Bo
authors.initials: TB
authors.lastname: Jensen
authors.forename: Lars
authors.initials: L
authors.lastname: Køber
authors.forename: Gunnar
authors.initials: G
authors.lastname: Gislason
authors.forename: Christian
authors.initials: C
authors.lastname: Torp-Pedersen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003718:Denmark / Q000453:epidemiology; D005220:Fathers / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008423:Maternal Age; D008875:Middle Aged; D009035:Mothers / Q000706:statistics & numerical data; D009203:Myocardial Infarction / Q000453:epidemiology / Q000235:genetics*; D010331:Paternal Age; D010375:Pedigree; D012189:Retrospective Studies; D012307:Risk Factors; D035781:Siblings; D055815:Young Adult