Mounting interest over the past 10 or 15 years in the possible role of infection in the risk of myocardial infarction (MI) has mainly centred on serological evidence of infection that often has occurred several years or months previously.¹ However, recent rather than distant infection may be more strongly associated with coronary events, as shown by the excess of coronary deaths in the winter months not accounted for by the concomitant increase in deaths from respiratory disease.² The most suggestive evidence comes from two studies carried out through the General Practice Research Database (GPRD).^3,4 In the first, the adjusted odds ratio (OR) for MI within 10 days of a respiratory infection was 3.0 (95% confidence interval (CI) 2.1 to 4.4, p < 0.0001) and was nearly 4.0 within five days of infection. In the second study, incidence ratios for MI were 4.95, 3.20, 2.81, and 1.95 at days 1–3, 4–7, 8–14, and 15–28 after infection, respectively. We therefore carried out a clinical case–control study, collecting information directly from patients admitted with MI and matched controls through a structured questionnaire to try to confirm or refute the indications of the GPRD studies based on documentary information.

METHODS

Cases were recruited from patients admitted with a clinical diagnosis of MI to the coronary care units at two hospitals. Potential controls were recruited from neighbouring general practices matched for age, sex, and area deprivation score. In total 119 cases and 214 matched controls were …