In the long human struggle against the slow erosion of mind, a seven-year trial across hundreds of rural Chinese villages offers a rare and grounded form of hope: that something as manageable as blood pressure, when carefully controlled by community health workers rather than specialists, can meaningfully reduce the likelihood of dementia. With 57 million people currently living with the condition and projections pointing toward 153 million by 2050, the question of what can be prevented has never carried more weight. This trial, enrolling nearly 34,000 people and spanning both active intervent