Healthy brain aging: effect of head injury, alcohol and environmental toxins.

Head injury has been recognized as an increasingly important determinant of late-life cognitive function. Despite a large number of research and clinical studies, no direct link has been established between minor head trauma with or without loss of consciousness and the development of dementia of the Alzheimer type. Similarly for alcohol, low doses have been found to be somewhat protective against dementia, whereas large doses increased the risk of late-life cognitive dysfunction. Among the many environmental toxins suspected of causing cognitive dysfunction, lead intoxication has the strongest evidence to support a link.