| Comments |
p.2005 left column 2nd paragraph:"Some measurable nonfocal structural losses occur with aging and are presumably related to these cognitive losses. Between the ages of 20 and 90, there is an average decrease of about 9.5% in the number of cortical neurons [primary source]. Averaged over a lifetime, this would represent a decline of about 85,000 neurons per day, or about 1 neuron per second. Even more striking, 40 to 50% of the myelinated nerve fiber length is lost in the old-old. In addition, vascular risk factors increase the loss of brain tissue and cognitive function over time." See BNID 113114 |