Table 1

Summary table of case–control studies of the association between laboratory-diagnosed influenza infection and AMI

StudyStudy locationStudy design and study periodParticipant age
Mean (range) *
Prior AMI in study participantsInfluenza in cases
n/N (%)
Influenza in controls
n/N (%)
OR (95% CI)Confounders adjusted forVaccine coverageaOR (95% CI)Risk of bias score
Guan et al29ChinaProspective hospital-based study; 2005–2006 and 2006–2007 influenza seasonsCases: 57.29 (SD 9.88)
Controls: 55.54 (SD 10.95)
Cases: prior MI and angina pectoris excluded
Controls: confirmed CAD or indications of CAD on an
ECG and CXR excluded
88/102 (86.3) for influenza A
78/102 (76.5) for influenza B
100/150 (66.7) for influenza A
45/150 (30.0) for influenza B
3.1 (1.5 to 6.4) for influenza A
10.2 (5.7 to 20.0) for influenza B
Demographics (age, education, employment, gender, insurance); CAD risk (BMI, HT, DM, family history, current smoking); biochemistry (HDL, LDL, total cholesterol, triglyceride); antibodies (influenza A/B, HSV 1/2, adenovirus, rubella, chlamydia)Estimated at 2%5.5 (1.3 to 23.0) influenza A
20.3 (5.6 to 40.8) influenza B
MacIntyre et al27Sydney, AustraliaProspective hospital-based study; 2008–2010 influenza seasonsAged ≥40 yearsCases: prior AMI eligible (NNR)
Controls: 12-month history of AMI, TIA or stroke excluded
53/275 (12.4)19/284 (1.97)1.97 (1.09 to 3.54)Age, gender, smoking, high cholesterol, influenza vaccination33.5% cases
64.8% controls
1.07 (0.53 to 2.19)Low
Ponka et al26Helsinki, FinlandProspective hospital-based study; 1980 influenza seasonCases: 63 (36–82)
Controls: 68 (33–89)
Exclusion criteria not reported3/49 (6.1)4/37 (10.8)0.54 (0.11 to 2.57)†Date of hospital admissionNot reportedNot calculatedHigh
Warren-Gash et al28London, EnglandProspective hospital-based study; 2009–2010 influenza seasonAged ≥40 years
63.6 (IQR 53.3–72.6)
Cases: prior AMI eligible (14/70)
Controls: 1-month history of AMI excluded (5/64 prior AMI)
25/70 (46.3)28/64 (54.9)0.7 (0.33 to 1.54)Influenza vaccination, personal and family history of AMI42.9% cases
45.3% controls
0.82 (0.34 to 2.00)Low
  • *Unless otherwise reported. †Calculated from included data (not reported in original paper).

  • AMI, acute myocardial infarction; aOR, adjusted OR; BMI, body mass index; CAD, coronary artery disease; CXR, chest X-ray; DM, diabetes mellitus; HDL, high-density lipoprotein; HSV, herpes simplex virus; HT, hypertension; LDL, low-density lipoprotein; MI, myocardial infarction; NNR, number not reported; TIA, transient ischaemic attack SD, standard deviation.