The World Health Organization (WHO) releases updated global guidelines on reducing the risk of cognitive decline and dementia across the life course. WHO says dementia is caused by brain diseases and affects memory, thinking and the ability to function. It estimates that more than 57 million people live with dementia worldwide and that nearly 10 million are newly diagnosed each year. WHO also notes that Alzheimer disease is the most common type, accounting for an estimated 60–70% of cases. The guidance emphasizes that while there is no cure, up to 45% of dementia risk could be prevented or delayed by addressing modifiable factors. These include tobacco use, harmful alcohol use, social isolation, physical inactivity, air pollution, and noncommunicable diseases such as high blood pressure and diabetes. The recommendations cover lifestyle and health interventions, including increased physical activity, stopping tobacco, reducing alcohol, adopting a healthy diet, and managing cardiometabolic conditions. WHO also includes approaches such as cognitive stimulation and engagement in social activities for adults with normal cognition or mild cognitive impairment, and states that hearing aids may be offered as part of risk-reduction strategies. The guidelines advise against vitamin B and E supplements, omega-3 supplements and multivitamins/minerals when no deficiency is diagnosed, citing lack of evidence for benefit.