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In this chapter, Moffat reviews observational research in older men that examines serum testosterone concentrations in relation to cognitive aging or Alzheimer's disease (AD) risk. Prospective cohort studies, such as the Baltimore Longitudinal Study of Aging, provide particularly useful data. Despite methodological limitations and conflicting findings, Moffat tentatively concludes that age-associated reductions in testosterone concentrations are a risk factor for cognitive decline and dementia. Cognitive vulnerability may be limited to specific domains of cognitive performance and may be modified by apolipoprotein E genotype. As he suggests, more definitive answers may require well designed randomized clinical trials that target cognitive effects of testosterone therapy. Any future trial must also consider other health outcomes that may be beneficially or adversely affected by testosterone.
Recent studies have reported significant atrophy of the corpus callosum (CC) in Alzheimer's Disease (AD). However, it is currently unknown whether CC atrophy is associated with specific cortical volume changes in AD. Moreover, possible atrophy in extra-callosal commissures has not been examined to date. The purpose of the present study was to quantify atrophy in two cerebral commissures [the CC and the anterior commissure (AC)], to correlate this measure with cognitive status, and to relate commissural size to independent measures of temporal lobe volume in AD patients.
A sample of AD patients and of age- and education-matched normal control subjects (NCs) underwent MRI and a cognitive test battery including the Dementia Rating Scale and Mini Mental State examination. Mid-sagittal regional areas within CC and AC were measured along with superior, middle and inferior temporal lobes volumes.
Alzheimer's Disease patients had significantly smaller callosa than did NCs. The callosal regions most affected in AD included the midbody, isthmus and genu. The isthmus and midbody areas of the CC were positively correlated with cognitive performance and with superior temporal lobe volume in AD patients. The mid-sagittal area of the AC and the superior temporal volumes did not differ between AD patients and NCs.
The study demonstrated that the regional morphology of the CC correlates with current cognitive status and temporal lobe atrophy in AD. As well, the lack of difference for the AC suggests that commissural atrophy in AD is regionally specific.
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