Summary table of case–control studies of the association between laboratory-diagnosed influenza infection and AMI
| Study | Study location | Study design and study period | Participant age Mean (range) * | Prior AMI in study participants | Influenza in cases n/N (%) | Influenza in controls n/N (%) | OR (95% CI) | Confounders adjusted for | Vaccine coverage | aOR (95% CI) | Risk of bias score |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Guan et al29 | China | Prospective hospital-based study; 2005–2006 and 2006–2007 influenza seasons | Cases: 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 | Moderate |
| MacIntyre et al27 | Sydney, Australia | Prospective hospital-based study; 2008–2010 influenza seasons | Aged ≥40 years | Cases: 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 vaccination | 33.5% cases 64.8% controls | 1.07 (0.53 to 2.19) | Low |
| Ponka et al26 | Helsinki, Finland | Prospective hospital-based study; 1980 influenza season | Cases: 63 (36–82) Controls: 68 (33–89) | Exclusion criteria not reported | 3/49 (6.1) | 4/37 (10.8) | 0.54 (0.11 to 2.57)† | Date of hospital admission | Not reported | Not calculated | High |
| Warren-Gash et al28 | London, England | Prospective hospital-based study; 2009–2010 influenza season | Aged ≥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 AMI | 42.9% 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.