MAPT and Cognitive impairment: It is known that a considerable proportion of people dying in old age without cognitive impairment have a substantial load of amyloid‐β and abnormal tau protein, considered to be the hallmarks of AD, in their brains.8 In contrast, these changes are not always found in those dying at a greater age with clear symptoms of dementia, which was clinically diagnosed as Alzheimer’s dementia.9 Moreover, of those with MCI, only 5–15% develop dementia per year, depending on the population under study.