Infections and brain health in ageing populations

A single bout of flu or a urinary tract infection could accelerate cognitive decline or trigger depression in an older person, and this project will find out how and why. Depression and dementia already affect 7% and 5% of adults over 60 respectively, and the global population is ageing fastest in Asia and Latin America. Infections are a potentially modifiable contributor to poor brain health, but their role is under-recognised and likely varies across settings. Current evidence is largely observational and cannot distinguish cause from coincidence. This research will apply robust causal inference methods—including Mendelian randomisation and causal mediation analysis—to large longitudinal datasets from the UK, US, Mexico, and India. By combining electronic health records, harmonised surveys, and UK Biobank’s genetic and social data, the team will ask three questions: what risks acute infections pose to brain health in the UK and US; whether those relationships differ in Mexico or India; and what biological or social pathways mediate them. If successful, the work will identify which infections matter most for brain ageing, and in which populations. That could inform targeted vaccination programmes, infection control in care homes, or clinical guidelines for treating infections in older adults—interventions that are already available but not yet deployed for brain health. The findings will also provide fundamental insights into how systemic inflammation affects the ageing brain across diverse global settings.