The research breakthrough ends decades of failure and shows a new era of drugs to treat Alzheimer's - the most common form of dementia - is possible. Yet the medicine, lecanemab, has only a small effect and its impact on people's daily lives is debated. And the drug works in the early stages of the disease, so most would miss out without a revolution in spotting it. Lecanemab attacks the sticky gunge - called beta amyloid - that builds up in the brains of people with Alzheimer'...