Evidence insufficient on relationship
of modifiable factors with risk of Alzheimer's disease
The available evidence is insufficient to draw firm conclusions
about the association of modifiable factors and risk of Alzheimer's disease (AD),
according to a report posted online today that will appear in the September issue
of Archives of Neurology, one of the JAMA/Archives journals.
Estimates suggest that up to 5.3 million people in the United States may have
AD, and this number will likely increase as baby boomers grow older. In fact,
"age is currently the strongest known risk factor for AD," write the
authors. Variation in the apolipoprotein E (APOE) gene is also associated with
the risk of developing AD. However, existing research to ascertain other risk
factors for the condition has been less conclusive.
From April 26 to 28, 2010, the National Institutes of Health convened a State-of-the-Science
Conference to examine studies of potential AD risk factors and possible preventive
measures. The conference evaluated existing English-language research found in
MEDLINE and the Cochrane Database of Systematic Reviews from 1984 through October
27, 2009, as well as a formal evidence report. Topics considered were nutritional
supplements and dietary factors, physical activity, other chronic conditions (diabetes,
high cholesterol, high blood pressure), substance use (cigarettes, alcohol), and
cognitive engagement. Panelists weighed the level of evidence for each risk factor
(low, moderate or high) and rated studies accordingly (low for observational studies
vs. high for randomized controlled trials).
Martha L. Daviglus, M.D., Ph.D., from Northwestern University Feinberg School
of Medicine, Chicago, and colleagues summarized the panel's findings. The group
determined "that currently there is no evidence of even moderate scientific
quality supporting the association of any modifiable factor with reduced risk
of cognitive decline or AD." While some studies appeared to show an increase
or reduction of AD risk or progression, they were not strong enough to draw firm
conclusions. The authors call for large-scale, long-term, population-based studies
and clinical trials to answer these questions. "It is hoped that the panel's
report will instigate rigorous high-quality research that can provide conclusive
evidence on this issue," they write. "Until more conclusive results
are available, individuals should continue to aim for a physically and mentally
active and healthy lifestyle and prevention of the well-known major risk factors
for chronic diseases."
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