Alzheimer’s

[Michael Scally MD]

Lv W, Du N, Liu Y, Fan X, Wang Y, et al. Low Testosterone Level and Risk of Alzheimer's Disease in the Elderly Men: a Systematic Review and Meta-Analysis. Mol Neurobiol. http://link.springer.com/article/10.1007/s12035-015-9315-y

Sex steroids can positively affect the brain function, and low levels of sex steroids may be associated with worse cognitive function in the elderly men. However, previous studies reported contrary findings on the relationship between testosterone level and risk of Alzheimer's disease in the elderly men.

The objective of this study was to comprehensively assess the relationship between low testosterone level and Alzheimer's disease risk in the elderly men using a meta-analysis. Only prospective cohort studies assessing the influence of low testosterone level on Alzheimer's disease risk in elderly men were considered eligible.

Relative risks (RRs) with 95 % confidence intervals (95 % CI) were pooled to assess the risk of Alzheimer's disease in elderly men with low testosterone level. Seven prospective cohort studies with a total of 5251 elderly men and 240 cases of Alzheimer's disease were included into the meta-analysis. There was moderate degree of heterogeneity among those included studies (I 2 = 47.2 %).

Meta-analysis using random effect model showed that low plasma testosterone level was significantly associated with an increased risk of Alzheimer's disease in elderly men (random RR = 1.48, 95 % CI 1.12-1.96, P = 0.006). Sensitivity analysis by omitting one study by turns showed that there was no obvious change in the pooled risk estimates, and all pooled RRs were statistically significant.

This meta-analysis supports that low plasma testosterone level is significantly associated with increased risk of Alzheimer's disease in the elderly men. Low testosterone level is a risk factor of worse cognitive function in the elderly men.

 

[Michael Scally MD]

A New Infectious Mechanism for Alzheimer’s?
https://blogs.sciencemag.org/pipeline/archives/2019/01/25/a-new-infectious-mechanism-for-alzheimers

We have another entry in the “Is Alzheimer’s caused by infectious disease?” drawing, and it’s a good one. A large multicenter team reports that Porphyromonas gingivalis, which is the key pathogen in gingivitis (gum disease) may be the actual causative agent in Alzheimer’s, which is a bold claim indeed. But they have several lines of evidence to back it up, and it’s a hypothesis that has to be taken seriously.

This particular idea has been developing out there already. Here’s a 2016 study looking at Alzheimer’s patients with peridontitis and finding that infected patients had more rapid cognitive decline. And this 2015 paper reported that gum disease was associated with higher amyloid levels in the normal elderly as well. In 2017, it was shown that deliberate infection gum-disease bacteria caused amyloid pathology and cognitive decline in a transgenic mouse model. This new paper draws quite a few more connecting lines – here we go: …

 

[Michael Scally MD]

Testosterone and Cognitive Impairment or Dementia in Middle-Aged or Aging Males

Background and purpose: To investigate the association between testosterone levels and the risk of dementia and to assess the effectiveness of testosterone supplement treatment in patients with cognitive impairment or dementia.

Methods: We searched Pubmed, Cochrane Library, and EMBASE on September 30, 2019.

Results: The risk factor portion of the review included 27 studies with 18 599 participants. Studies revealed inconsistent findings on the association between testosterone levels and the risk of all-cause dementia or Alzheimer disease (AD).

The result from our meta-analysis showed an increased risk of all-cause dementia with decreasing total testosterone (total-T, 4572 participants, hazard ratio: 1.14, 95% CI: 1.04-1.26). Some studies also found an increased risk of AD with a lower level of total-T, free testosterone, and bioavailable testosterone.

Testosterone supplement treatment may improve general cognitive function and motor response in the short term as measured by the Developmental Test of Visual-Motor Integration (mean difference [MD]: 4.4, 95% CI: 1.20-7.59) and the Mini-Mental State Examination (MD: 3.4, 95% CI: 0.83-5.97) and verbal memory as measured by story recall delay at 3 months (MD: 8.4, 95% CI: 0.49-16.3).

Conclusion: Lower levels of testosterone may be associated with an increased risk of all-cause dementia or AD. Testosterone supplement treatment may or may not improve general cognitive function in patients with cognitive impairment/AD.

Zhang Z, Kang D, Li H. Testosterone and Cognitive Impairment or Dementia in Middle-Aged or Aging Males: Causation and Intervention, a Systematic Review and Meta-Analysis [published online ahead of print, 2020 Jun 30]. J Geriatr Psychiatry Neurol. 2020;891988720933351. doi:10.1177/0891988720933351 SAGE Journals: Your gateway to world-class research journals

 

[Michael Scally MD]