Family history of myocardial infarction and cause-specific risk of myocardial infarction and venous thromboembolism: the Tromsø Study.

Background: A family history of myocardial infarction (FHMI) has been shown to increase the risk of venous thromboembolism (VTE). The mechanism underlying the association remains unclear. Therefore, we aimed to determine the risks of MI and VTE by FHMI using a cause-specific model and to explore whether atherosclerotic risk factors could explain the association between FHMI and VTE in a population-based cohort.

Methods And Results: The study included 21 624 subjects recruited from the Tromsø Study in 1994 to 1995 and 2001 to 2002. Incident MI and VTE events were registered from date of enrollment to end of follow-up, December 31, 2010. There were 1311 MIs and 428 VTEs during a median follow-up of 15.8 years. FHMI was associated with a 52% increased risk of MI (adjusted hazard ratio, 1.52; 95% confidence interval, 1.35-1.70) and a 26% increased risk of VTE (adjusted hazard ratio, 1.26; 95% confidence interval, 1.02-1.55) in the cause-specific Cox model. Similar results were found using the traditional Cox model. The risk estimates by status of FHMI were highest for unprovoked deep vein thrombosis (adjusted hazard ratio, 1.69; 95% confidence interval, 1.12-2.56), and the risk increased with increasing number of affected relatives. Modifiable atherosclerotic risk factors slightly altered the association between FHMI and MI but had a negligible effect on the association between FHMI and VTE.

Conclusions: FHMI was associated with increased risk of both MI and VTE in a cause-specific model. Apparently, the association between FHMI and VTE applied to unprovoked deep vein thrombosis and was not explained by modifiable atherosclerotic risk factors.