Scientists from the University of South Florida and the University of Kentucky report that people who develop Alzheimer's disease may show signs of this illness many decades earlier in life, including compromised educational achievement.
Their research appears online this month in the journal Alzheimer's Disease and Associated Disorders.
Participants in the Nun Study were studied to identify those who became demented before death or had characteristic brain changes of Alzheimer's disease at autopsy. Among nuns who became demented or had evidence of Alzheimer's disease at autopsy, those with small head sizes had significantly lower educational achievement in earlier adult life. In those dying without a dementia diagnosis or autopsy evidence of Alzheimer's disease, head size had no relationship with education.
Adult head size can be used to estimate the size of the fully-developed brain. Previous studies have found that clinical expression of Alzheimer's disease is related to head size, with people having smaller heads more likely to show the characteristic symptoms of this illness. Larger brains provide reserve against Alzheimer's, allowing people to function normally despite having considerable Alzheimer pathology in their brains.