Three other studies reported at AAIC 2013 illuminate Alzheimer's risk factors,
point to potential new strategies for treatment, prevention
BOSTON, July 15, 2013 /PRNewswire-USNewswire/ -- Most kinds of cancer are
associated with a significantly decreased risk of Alzheimer's disease, according
to a study of 3.5 million veterans reported today at the Alzheimer's Association
International Conference(R) 2013 (AAIC(R) 2013) in Boston. In addition, the
study suggested that chemotherapy treatment for almost all of those cancers
conferred an additional decrease in Alzheimer's risk.
Three other researchers presented results of epidemiologic studies that
uncovered risk factors and/or possible therapies for Alzheimer's disease. The
results indicated that:
-- Metformin, a medication for type 2 diabetes, may be linked with lower
Alzheimer's risk among type 2 diabetes patients compared with other
-- Older age at retirement appears to be associated with reduced
-- Socioeconomic disparities may account for the previously observed
increased risk of Alzheimer's among African Americans.
"With these large-cohort studies and others, we are beginning to see the
outlines of a broad picture of Alzheimer's disease risk and prevention factors,"
said Maria Carrillo, Ph.D., vice president of medical and scientific relations
at the Alzheimer's Association.
"However, we need to know even more about what specific factors actually raise
and lower risk for cognitive decline and Alzheimer's. To do that, we need
longer-term studies in larger and more diverse populations, and more research
funding is required to make that happen. Alzheimer's research would benefit from
its own version of the Framingham Study, which has taught us so very much about
preventable risk factors for heart disease and stroke," Carrillo said.
"With funding of research being a critical need for progress, the National Plan
to Address Alzheimer's Disease must be fully implemented and the $100 million
identified for Alzheimer's and dementia research this fiscal year needs to be
funded," Carrillo concluded.
Cancer history and chemotherapy are associated with decreased risk of
A growing body of evidence suggests a possible association of cancer with
reduced risk for Alzheimer's disease; until now, whether the association differs
between cancer types or is modified by cancer treatment is unknown.
Laura Frain, M.D., a geriatrician at VA Boston Healthcare System, and colleagues
analyzed the health records of 3,499,378 veterans age 65 and older who were seen
in the VA health care system between 1996 and 2011 and who were free of dementia
at baseline. The objective was to evaluate the relationship between a history of
19 different cancers, cancer treatment and subsequent Alzheimer's disease.
Over a median follow-up of 5.65 years, 82,028 veterans were diagnosed with
Alzheimer's. Twenty-four (24) percent of those veterans with Alzheimer's had a
history of cancer, while 76 percent did not.
The researchers found that most types of cancer were associated with reduced
Alzheimer's risk, ranging from 9 percent to 51 percent. Reduced risk was
greatest among survivors of liver cancer (51 percent lower risk), cancer of the
pancreas (44 percent), cancer of the esophagus (33 percent), myeloma (26
percent), lung cancer (25 percent) and leukemia (23 percent). Cancers that did
not confer a reduced Alzheimer's risk, or were associated with an increased
risk, included melanoma, prostate and colorectal cancers.
The researchers found no association between cancer history and reduced risk of
any other typical age-related health outcome; in fact, cancer was associated
with an increased risk of stroke, osteoarthritis, cataracts and macular
degeneration. Most cancer survivors were also at increased risk for
"Together, these findings indicate that the protective relationship between most
cancers and Alzheimer's disease is not simply explained by increased mortality
among cancer patients," said Frain. "More research is needed to determine if
these results have therapeutic implications for Alzheimer's."
Among veterans with a cancer history, treatment with chemotherapy but not
radiation reduced Alzheimer's risk by 20 to 45 percent, depending on cancer
type, with the exception of prostate cancer.
"The potential protective effect of chemotherapy is supported by recent
experimental studies," Frain observed. "The results of this study are
interesting because they could help focus future research onto the specific
pathways and treatment agents involved in the individual cancers that are
associated with a reduced risk of Alzheimer's. This could potentially open new
therapeutic strategies for Alzheimer's prevention and treatment."
Metformin is linked with lower dementia risk than other type 2 diabetes
Type 2 diabetes doubles the risk of dementia. However, until recently, little
research has been done to examine the association between type 2 diabetes
treatments and dementia risk. Rachel Whitmer, Ph.D., and colleagues at Kaiser
Permanente Division of Research studied a cohort of 14,891 type 2 diabetes
patients age 55 and older who began diabetes therapy between October 1999 and
November 2001. Only patients who started a single therapy (metformin,
sulfonylureas, thiazolidinediones (TZDs) or insulin) were included. The patients
were followed for up to five years.
Patients initiating metformin, an insulin sensitizer, had a significantly
reduced risk of developing dementia compared with patients on other diabetes
therapies. Compared with those taking sulfonylureas, those initiating metformin
had a 20 percent reduced risk of dementia, while those initiating TZD or insulin
had no difference in risk.
"These results provide preliminary evidence that the benefits of insulin
sensitizers may extend beyond glycemic control to neurocognitive health," said
Whitmer. "Research in animals suggests that metformin may contribute to the
creation of new brain cells and enhance spatial memory."
Trials are currently under way to evaluate metformin as a potential therapy for
dementia and mild cognitive impairment, which is thought to be, in some cases, a
precursor to Alzheimer's disease.
Older age at retirement is associated with reduced risk of dementia
Some research has suggested that intellectual stimulation and mental engagement
throughout life may be protective against Alzheimer's disease and other
dementias. In an analysis of health and insurance records of more than 429,000
self-employed workers in France, reported at AAIC 2013, Carole Dufouil, Ph.D.,
director of research in neuroepidemiology at INSERM (Institut National de la
sante et de la recherche medicale) at the Bordeaux School of Public Health, and
colleagues found that retirement at older age is associated with a reduced risk
The researchers linked health and pension databases of self-employed workers who
were living and retired as of December 31, 2010. Workers had been retired on
average for more than 12 years. Prevalence of dementia in this group was 2.65
Analyses showed that the risk of being diagnosed with dementia was lower for
each year of working longer (i.e., higher age at retirement) (hazard ratio of
dementia was 0.968 (95 percent Confidence Interval = [0.962-0.973]). Even after
excluding workers who had dementia diagnosed within the 5 years following
retirement, the results remained unchanged and highly significant (p<0.0001).
"Our data show strong evidence of a significant decrease in the risk of
developing dementia associated with older age at retirement, in line with the
'use it or lose it' hypothesis," said Dufouil. "The patterns were even stronger
when we focused on more recent birth cohorts."
"Professional activity may be an important determinant of intellectual
stimulation and mental engagement, which are thought to be potentially
protective against dementia," observed Dufouil. "As countries around the world
respond to the aging of their populations, our results highlight the importance
of maintaining high levels of cognitive and social stimulation throughout work
and retired life, and they emphasize the need for policies to help older
individuals achieve cognitive and social engagement.
The study was also coordinated by the International Longevity Center-France
(Head: Prof. Francoise Forette).
Socioeconomic disparities may explain higher Alzheimer's risk among African
Alzheimer's disease and other dementias have been shown to be higher among older
blacks in the United States than older whites; however, risk factors that might
account for this difference have not been extensively studied.
Note: According to the Alzheimer's Association 2013 Alzheimer's Disease Facts
and Figures report, older African-Americans are about twice as likely to have
Alzheimer's and other dementias as older whites, and Hispanics are about one and
one-half times as likely to have Alzheimer's and other dementias as older
Kristine Yaffe, M.D., of the University of California, San Francisco and the San
Francisco VA Medical Center, and colleagues sought to determine if differences
in dementia rates by race existed among a cohort of community dwelling elders
and whether any differences observed could be explained by socioeconomic status
(SES) indicators (income, financial adequacy, education and literacy) and
The scientists evaluated dementia risk among 3,075 black and white elders (mean
age 74.1 years) participating in the ongoing prospective Health, Aging and Body
Composition Study who were free of dementia at baseline.
During 12 years of follow-up, 18.7 percent of participants were determined to
have developed dementia, based on prescribed medications, hospital records and
cognitive decline. In this population, African-Americans were 1.5 times more
likely to develop dementia than whites (21.9 percent vs. 16.4 percent). However,
after adjusting for socioeconomic factors including education level, literacy,
income and financial adequacy, the researchers found that the difference in risk
was no longer statistically significant.
"Our findings suggest that differences in socioeconomic factors may, in large
part, explain racial and ethnic disparities in dementia rates," said Yaffe.
"Future studies that investigate these disparities should take a broad range of
socioeconomic factors into account."
Yaffe suggested that more studies are needed "to explore the potential benefits
of improving socioeconomic risk factors as a way of reducing dementia rates."
(Disclosure: Dr. Yaffe is co-chair of the AAIC 2013 Program Committee.)
The Alzheimer's Association International Conference (AAIC) is the world's
largest conference of its kind, bringing together researchers from around the
world to report and discuss groundbreaking research and information on the
cause, diagnosis, treatment and prevention of Alzheimer's disease and related
disorders. As a part of the Alzheimer's Association's research program, AAIC
serves as a catalyst for generating new knowledge about dementia and fostering a
vital, collegial research community.
About the Alzheimer's Association
The Alzheimer's Association is the world's leading voluntary health organization
in Alzheimer care, support and research. Our mission is to eliminate Alzheimer's
disease through the advancement of research; to provide and enhance care and
support for all affected; and to reduce the risk of dementia through the
promotion of brain health. Our vision is a world without Alzheimer's. Visit
www.alz.org or call 800.272.3900.
SOURCE Alzheimer's Association