EHJ: Respiratory infections linked to heart attack and stroke risks

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Respiratory infections double the risk of major cardiovascular events for myocardial infarction (MI) or stroke, especially within a week of the infection, according to a study in the December issue of the European Heart Journal.

Timothy Clayton, MSc, and colleagues, from the medical statistics unit at the London School of Hygiene & Tropical Medicine in London, collected information from the IMS Disease Analyzer Mediplus primary care database. The database is used widely in epidemiological research with recorded contacts of about two million patients with approximately 500 general practitioners.

Clayton and colleagues examined 11,155 cases on the IMS database with a first-time diagnosis of MI who met the inclusion criteria of whom 61 percent were men (mean age 71 years) and 39 percent women (mean age 79 years). There were 9,208 cases with a first-time diagnosis of stroke of whom 45 percent were men (mean age 76 years) and 55 percent women (mean age 81 years).

For MI and stroke respectively, there were 326 and 260 respiratory infections during the month preceding the index date. There was strong evidence of an increased risk of both events in the seven days following infection, for MI adjusted odds ratio (OR) of 2.1, for stroke OR 1.92. The strength of the associations dropped off after a greater amount of time had passed. The associations for MI occurred at all levels of initial underlying cardiovascular risk, according to Clayton and his colleagues. 

They also reported that there was no evidence of a link between body mass index (BMI) and risk of stroke, and adjustment for BMI had no impact on the association between respiratory infection and stroke. There was also no evidence of an association between vaccination against influenza and pneumococcal disease with risk of MI or stroke.

The researchers concluded that “aborting or preventing attacks of influenza will reduce vascular events and there are some studies suggesting that this is so, although the evidence is still not conclusive.”

They did recommend that reducing respiratory infection, particularly during the winter months, could substantially reduce the number of vascular deaths attributable to respiratory infection.