Nowadays, there are very effective treatments for many serious illnesses. But there is still no sign of an effective treatment, let alone a cure, for dementia – especially Alzheimer’s disease. And how could there be, when even the experts don’t agree on the cause? Defective tau proteins, some say, while others believe the blame lies with a type of protein called amyloid beta that has clumped together into threadlike shapes known as fibrils.