Investigating causal relationships between urinary tract infection and acute myocardial infarction or stroke

This project will investigate causal relationships between urinary tract infection (UTI) and acute myocardial infarction (MI) or stroke.

Robust epidemiological evidence of a causal relationship will widen our understanding of cardiovascular disease mechanisms and justify and inform clinical trials of prevention strategies. We hypothesise that the risk of MI or stroke is greater following microbiologically confirmed UTI.

To test this hypothesis, we will use anonymised linked healthcare data to conduct self-controlled case series studies in which individuals act as their own controls, thereby eliminating time invariant confounding. Cases will be patients aged ≥30 with an MI or stroke identified from inpatient hospital data.

The exposure period will last up to 90 days after the date of a UTI. We will ascertain UTI using linked microbiology, general practice, and inpatient hospital data.

We will calculate the incidence of MI or stroke during exposed and unexposed periods and use conditional Poisson regression to estimate Incidence Rate Ratios (IRRs) with 95% confidence intervals adjusted for time varying confounders.

Additional analyses will estimate risk for clinically important sub-groups and investigate the causal role of different urinary pathogens. Several sensitivity analyses will enable triangulation of findings and support robust and reliable causal inferences.