• DEMENTIA

Dementia, the most feared accompaniment of ageing, already affects more than 900 000 people in the UK, with numbers predicted to rise rapidly in line with increasing life expectancy.1 As the scale of the coming epidemic with its attendant financial implications becomes clear, dementia prevention becomes ever more a priority for governments, and individuals increasingly want to know what they can do to modify their risk.

Evidence linking a variety of potential risk factors for dementia comes predominantly from observational and epidemiological studies alongside some clinical trials, which have been synthesised in several comprehensive analyses, the best known of which is the Lancet Commission on Dementia. First published in 20172 and revised in 2020,3 this identifies 12 potentially modifiable risk factors acting at different stages of life that together might explain ~40% of worldwide dementia risk. In early life, the principle risk is low education. In mid-life (defined as ages 45–65 years) these are obesity, excess alcohol, traumatic brain injury, hearing loss and hypertension; while in later life smoking, depression, social isolation, physical inactivity, diabetes mellitus and air pollution are implicated.

That such a significant proportion of dementia cases might be modifiable is cause for optimism at a time when therapeutic advances in dementia are few and far between. However, several important questions remain. What evidence is there to guide specific targets and interventions? How much modification can reasonably be expected in practice? What aspects of dementia are we preventing? And are there more risk factors to be determined?

When it comes to making recommendations, there is a relative lack of randomised controlled trial evidence to …