Summary table of case–control studies of the association between RTI and AMI
| Study | Study location | Study design and study period | Participant age Mean (range)* | Prior AMI in study participants | RTI in cases n/N (%) | RTI in controls n/N (%) | OR (95% CI) | Adjusted confounders | Vaccine coverage | aOR (95% CI) | Risk of bias score |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Clayton et al31 | Kansas, USA | Prospective hospital-based study; influenza season(s) unknown | 63 (NNR) | Exclusion criteria not reported | 177/335 (52.8) | 126/199 (63.3) | 1.0 (0.5 to 1.9) | Gender, age, BMI, area deprivation score, smoking status and history of angina | Not reported | 0.92 (0.60 to 1.42) | High |
| Clayton et al32 | UK | Retrospective GP database study; 1994–1996, not restricted to influenza season | 72 (SD 13) | Cases/controls: prior MI excluded | 84/11 155 (0.8)† | 34/11 155 (0.3)† | 2.48 (1.67 to 3.70)‡ | Hypertension, hyperlipidaemia, diabetes, CVA, coronary heart disease in first-degree relatives, peripheral vascular disease and chronic obstructive pulmonary disease, smoking status and BMI | 35.6% cases 31.7% controls | 2.55 (1.71 to 3.80) | Moderate |
| MacIntyre et al27 | Sydney, Australia | Prospective hospital-based study; 2009–2010 influenza seasons§ | Aged ≥40 years | Cases: prior AMI eligible. (NNR) Controls: 12-month history of AMI, TIA or stroke excluded | 52/275 (31.1) | 32/284 (18.6) | 1.98 (1.2 to 3.3) | Age, gender, smoking, high cholesterol | 33.5% cases 64.8% controls | Not calculated | Low |
| Meier et al33 | UK | Retrospective GP database study; 1994–1996, not restricted to influenza season | Aged ≤75 years | Cases/controls: prior MI, angina pectoris and other cardiovascular conditions excluded | 54/1922 (2.8)¶ | 72/7649 (0.94)¶ | 3.0 (2.1 to 4.4) | Smoking status, BMI, history of asthma, calendar year, fatal AMI | Not reported | 3.0 (2.1 to 4.4) | High |
| Penttinen and Valonen34 | Finland | Nested case–control study; 1980–1992 not restricted to influenza season | NNR (38–61) | Cases: exclusion criteria not reported Controls: prior MI excluded | 50/83 (60.3) | 115/249 (46.1) | 1.77 (1.07 to 2.93)‡ | Age, smoking status, social status and county of residence | Not reported | Not calculated | High |
| Spodick et al35 | Massachusetts, USA | Prospective hospital-based study; influenza season(s) unknown | Cases: males 63 (SD 13), females 73 (SD 11) Controls: males 63 (SD 13), females 73 (SD 11) | Exclusion criteria not reported | 42/150 (28) | 23/150 (15.3) | 2.15 (1.22 to 3.80)‡ | Gender | 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) | 17/70 (24.3) | 12/64 (18.8) | 1.39 (0.60 to 3.19) | Influenza vaccination, personal and family history of AMI | 42.9% cases 45.3% controls | 1.39 (0.56 to 3.47) | Low |
*Unless otherwise reported.
†RTI occurring 1–7 days before AMI. ‡Calculated from included data (not reported in original paper).
§RTI questionnaires conducted over the 2009 and 2010 influenza seasons only.
¶RTI occurring 1–10 days before AMI.
AMI, acute myocardial infarction; BMI, body mass index; CVA, cerebrovascular accident; IQR, interquartile range; MI, myocardial infarction; NNR, number not reported; RTI, respiratory tract infection; TIA, transient ischaemic attack; SD, standard deviation.