People who are sick with flu are six times more likely to experience a heart attack the week after they test positive compared to the year before or the year after, researchers from the Netherlands will report at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) meeting in Copenhagen between Apr 15 and Apr 18.
Canadian researchers had reported the connection before, but the new study factors in death records, which include out-of-hospital heart attacks.
In the new study, researchers examined test results from 16 labs across the Netherlands, along with death and hospital records. Of 26,221 flu cases confirmed between 2008 and 2019, 401 people had at least one heart attack within one year of flu diagnosis. There were 419 heart attacks all together.
Of the 419 heart attacks, 25 occurred in the first 7 days after flu diagnosis, 217 in the year before and 177 in the year after, not counting the week after testing positive. Roughly one third died from any cause within a year of their flu diagnosis. The team calculated that people are 6.16 times more likely to have a heart attack in the week after flu diagnosis, similar to the 6.05 times greater risk that the Canadian group found, but at a level that translates to a weaker association of 2.42 times greater risk.
Flu infection can increase blood coagulation that, along with inflammation prompted by the immune response, could contribute to arterial plaque ruptures that lead to a heart attack, the researchers said.
Annemarijn de Boer, PhD, one of the study coauthors who is with the Julius Center for Life Sciences and Primary Care in Utrecht, said in an ECCMID press release that showing a more robust connection from a different population has important public health implications. "Our results endorse strategies to prevent influenza infection, including vaccination."