Familial effects on survival after myocardial infarction: a registry-based sib-pair study

The chance of surviving an acute myocardial infarction (MI) has increased greatly but many persons still die as a consequence of MI. We assessed the familiality of suffering fatal MI using Swedish registry data. All 4,239 sib-pairs (n = 8,478) where both siblings had suffered an MI and who were born 1932 or later were identified by matching the Swedish National Patient-, Cause of Death and Multi-Generation registries. The Cox proportional hazards model was used to estimate the association between survival times between sibling who had, or not had, a sibling who died within 28 days of their first MI. The risk estimate was adjusted for year of infarction, age at infarction, sex and county for both siblings. The mortality rate was increased the first 28 days after infarction amongst patients who had a sibling who also died within 28 days of infarction (adjusted Hazard ratio (HR) [95 % confidence interval [95 % CI]: 1.44 [1.18-1.75]). These patients also have a worse long-term survival (adjusted HR [95 % CI]: 1.65 [1.24-2.21]). There appears to be familial effects that influence MI survival. This may have important implications for MI prevention strategies but further studies are required to determine if these effects are due to genetic or environmental factors.