The World Health Organization has issued its most comprehensive guidance yet on dementia prevention, asserting that up to 45 per cent of risk can be prevented or delayed by tackling 14 modifiable factors across the life course. The update, released from Geneva, arrives as more than 57 million people live with dementia worldwide and nearly 10 million new cases are diagnosed each year. Alzheimer’s disease accounts for 60 to 70 per cent of those cases, and with no cure widely available, the agency has placed prevention at the centre of its strategy.

The guidelines, which replace a 2019 edition, draw on an expanded evidence base to recommend controlling hypertension, diabetes and high cholesterol; quitting tobacco and reducing alcohol intake; maintaining physical activity and social connections; and using hearing aids for age-related hearing loss. For the first time, the WHO also advises reducing exposure to air pollution. It explicitly counsels against vitamin B, E, omega-3 or multivitamin supplements in the absence of a diagnosed deficiency, noting that the evidence does not support their use for cognitive protection.

In a separate development, a phase 2 trial of the experimental drug diranersen has provided the first clinical signal that a therapy targeting the tau protein can slow cognitive decline. The study, presented at the Alzheimer’s Association International Conference in London, enrolled 416 people with mild cognitive impairment or mild Alzheimer’s dementia. Over 18 months, the antisense oligonucleotide reduced tau levels in cerebrospinal fluid by 50 to 65 per cent and slowed decline on the Mini-Mental State Examination by 50 per cent compared with placebo, though the trial did not meet its primary dose-response endpoint. Five of six clinical measures favoured the drug, and no cases of brain oedema were recorded. Biogen, the developer, plans to advance the therapy into phase 3.

Meanwhile, a blood test measuring the biomarker p-tau217 is sharpening the ability to predict who will develop cognitive impairment. A team at Harvard Medical School found that cognitively healthy older adults with elevated p-tau217 had a 38 per cent higher risk of progressing to mild cognitive impairment within five years. The test is not yet recommended for routine screening of asymptomatic individuals, but researchers view it as a step toward risk assessment tools analogous to cholesterol tests. The next milestones to watch are the launch of the phase 3 programme for diranersen and the adoption of the WHO’s prevention roadmap by national health systems.