Research Insights

Plasma testosterone levels in Alzheimer and Parkinson’s diseases

Okun, M., DeLong, M, Hanfelt, J., Gearing, M., & Levey, A.. (2004 Plasma testosterone levels in Alzheimer and Parkinson’s diseases , 2004 Feb 10;62(3):411-3

These authors cited research that suggests there is a link between testosterone deficiency and neurodegenerative diseases (e.g. PD and Alzheimer ‘s disease [AD]). As they have suggested in prior studies (see other Okun 2002 articles in CSR), testosterone deficiency may contribute to nonmotor symptoms seen in PD (mood, apathy, sexual functioning, etc.). Interestingly testosterone deficiency has also been linked to AD. To further study the link between these conditions, they studied 68 male patients with PD (mean age 66, education 16 years, and disease duration 11 years) and 50 male patients with AD (mean age 75, education 14 years, and disease duration 4 years). All patients had their plasma drawn to measure their testosterone levels and many of the patients also underwent select neuropsychological measures (e.g. attention, memory, language, mental flexibility, global cognitive functioning, and depression). During their analysis, the researchers accounted for age and education as there was a significant discrepancy between the groups on both variables. They found that testosterone levels did not significantly vary between the PD and AD groups. They did find that older men in both groups had lower testosterone levels than the younger patients but that decline was not greater than seen in a healthy age matched population (data compared to the Baltimore Longitudinal Study of elderly community-dwelling men). Generally there were no significant differences in the cognitive testing for either group related to their testosterone levels. These authors attempted to study the link between testosterone, cognition, and degenerative disease but were limited by their sample size for many of their comparisons (not all patients took all of the tests). Although their data did not clearly show a relationship, they suggested that based upon what is known about testosterone deficiency and neurodegenerative diseases,, this relationship needs to be studied further longitudinally with larger sample sizes.

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