Sex differences in incidence and mortality of bloodstream infections. Results from the population-based HUNT study in Norway

Objective To examine the effect of sex on risk of bloodstream infections (BSI) and BSI mortality and to assess to what extent known risk factors for BSI mediate this association in the general population. Participants The prospective, population-based HUNT2 Survey (1995-97) in Norway invited 93,898 inhabitants ≥20 years in the Nord-Trøndelag region, whereof 65,237 (69.5%) participated. 46.8% of the participants were men. Exposures Sex and potential mediators between sex and BSI; health behaviours (smoking, alcohol consumption), education attainment, cardiovascular risk factors (systolic blood pressure, non-HDL cholesterol, body mass index) and previous or current comorbidities. Main outcome measures Sex differences in risk of first-time BSI, BSI mortality (death within first 30 days after a BSI), BSI caused by the most frequent bacteria, and the impact of known BSI risk factors as mediators. Results We documented a first-time BSI for 1,840 (2.9%) participants (51.3% men) during a median follow-up of 14.8 years. Of these, 396 (0.6%) died (56.6% men). Men had 41% higher risk of any first-time BSI (95% confidence interval (CI), 28 to 54%) than women. An estimated 34% of the excess risk of BSI in men was mediated by known BSI risk factors. The hazard ratio (HR) with 95% CI for BSI due to S. aureus was 2.09 (1.28 to 2.54), S. pneumoniae 1.36 (1.05 to 1.76), and E. coli 0.97 (0.84 to 1.13) in men vs women. BSI related mortality was higher in men compared to women with HR 1.87 (1.53 to 2.28). Conclusions This large population-based study show that men have higher risk of BSI than women. One-third of this effect was mediated by known risk factors for BSI. This raises important questions regarding sex specific approaches to reduce the burden of BSI.