October 9, 2012Open Access
View Full PaperInfluenza Infection and Risk of Acute Myocardial Infarction in England and Wales: A CALIBER Self-Controlled Case Series Study
Key Result
Acute respiratory infection was associated with a significantly increased risk of acute myocardial infarction during days 1-3 after consultation (incidence ratio 4.19; 95% CI 3.18-5.53).
Study Design
Type
Observational (n=11,208)
Multicenter
Yes
Structured PICO
Does acute respiratory infection, specifically influenza, trigger acute myocardial infarction in adults aged ≥ 40 years?
P
Population
11,208 patients aged ≥ 40 years with a first acute myocardial infarction (AMI), of which 3,927 had also consulted for acute respiratory infection.
I
Intervention
Acute respiratory infection (specifically influenza and influenza-like illnesses)
C
Comparator
Baseline periods without acute respiratory infection (self-controlled case series design)
O
Outcome
Incidence of acute myocardial infarction (AMI) after consultation for acute respiratory infectionhard clinical
Acute respiratory infections, particularly influenza, significantly increase the short-term risk of acute myocardial infarction, highlighting a potential trigger for acute coronary events.
Main Result
Effect estimate: Incidence ratio 4.19 (95% CI 3.18-5.53)
Abstract
BACKGROUND: An association between infections and vascular events has been observed, but the specific effect of influenza and influenza-like illnesses on triggering acute myocardial infarction (AMI) is unclear. METHODS: Episodes of first AMI from 1 January 2003 through 31 July 2009 were identified using linked anonymized electronic medical records from the Myocardial Ischaemia National Audit Project and the General Practice Research Database. Self-controlled case series analysis was used to investigate AMI risks after consultation for acute respiratory infection. Infections were stratified by influenza virus circulation, diagnostic code, and vaccination status to assess whether influenza was more likely than other infections to trigger AMI. RESULTS: Of 22,024 patients with acute coronary syndrome, 11,208 met the criterion of having had their first AMI at the age of ≥ 40 years, and 3927 had also consulted for acute respiratory infection. AMI risks were significantly raised during days 1-3 after acute respiratory infection (incidence ratio, 4.19 95% confidence interval, 3.18-5.53, with the effect tapering over time. The effect was greatest in those aged ≥ 80 years (P = .023). Infections occurring when influenza was circulating and those coded as influenza-like illness were associated with consistently higher incidence ratios for AMI (P = .012). CONCLUSIONS: Influenza and other acute respiratory infections can act as a trigger for AMI. This effect may be stronger for influenza than for other infections. CLINICAL TRIALS REGISTRATION: NCT01106196.