Thursday, December 17, 2009

Appendix of Alzheimer's Essay

In this appendix, I include the full abstract of two papers that are relevant to the theory presented here. The first is the abstract of reference [19] in [46], which is reference [44] here [see the section on statin drugs above for context]:

Abstract, "Epidemiological and clinical trials evidence about a preventive role for statins in Alzheimer's disease:"

"This paper reviews epidemiological and clinical trials data about whether statin use reduces the risk of Alzheimer's disease (AD). The available information has come in three waves. The initial, mostly cross-sectional observational reports suggested that statins might prevent dementia. Next, two large clinical trials with cognitive add-on studies showed no benefit and neither did the third wave, again with observational studies. The latter were mostly longitudinal, and were critical of the first studies for not adequately addressing confounding by indication (i.e. that patients with dementia would be denied statins). Most recently, new data from the Canadian Study of Health and Aging have produced a mixed result. While methodological considerations are clearly important in understanding why the reports are so variable, there might also be merit in differentiating between statins, based on their presumed - and variable - mechanisms of action in dementia prevention, before concluding that the initial reports are entirely artefactual. Still, the first reports appear to have overestimated the extent of protection, so that unless there are important effects achievable with specific statins, a more than a modest role for statins in preventing AD seems unlikely."

The second abstract is taken from reference [28], on the "alternative hypothesis" that amyloid-beta is protective rather than detrimental to Alzheimer's, i.e., that it is a "protective response to neuronal insult:"

Abstract, "Amyloid-beta in Alzheimer disease: the null versus the alternate hypotheses:"

"For nearly 20 years, the primary focus for researchers studying Alzheimer disease has been centered on amyloid-beta, such that the amyloid cascade hypothesis has become the "null hypothesis." Indeed, amyloid-beta is, by the current definition of the disease, an obligate player in pathophysiology, is toxic to neurons in vitro, and, perhaps most compelling, is increased by all of the human genetic influences on the disease. Therefore, targeting amyloid-beta is the focus of considerable basic and therapeutic interest. However, an increasingly vocal group of investigators are arriving at an "alternate hypothesis" stating that amyloid-beta, while certainly involved in the disease, is not an initiating event but rather is secondary to other pathogenic events. Furthermore and perhaps most contrary to current thinking, the alternate hypothesis proposes that the role of amyloid-beta is not as a harbinger of death but rather a protective response to neuronal insult. To determine which hypothesis relates best to Alzheimer disease requires a broader view of disease pathogenesis and is discussed herein."

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