Alzheimer's - High
Estrogen Levels Linked To Dementia – Netherlands Study of Older Hawaiian
Men – No Association Found with Testosterone
July 24th 2006
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Estrogen Targets |
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Researchers from the Netherlands have found a link between high estrogen
levels and dementia in older men. Their data came from a group of 2974
Japanese-American men aged 70 to 91 who participated in the
Honolulu-Asia Aging Study. The baseline fasting blood samples were
drawn between 1991 and 1993, at which time levels of testosterone and
estradiol, the major estrogen in humans were measured.
None of the participants had signs of dementia at the beginning of the
study. The researchers measured cognitive decline or dementia in all
the participants in 1994-1996 and 1997-1999 using the Cognitive
Abilities Screening Instrument (CASI). They collected physical,
demographic and medical information at each exam.
Of the 2300 participants who completed the study, 223 were diagnosed
with incident dementia during the follow-up period. There were 134 men
who developed Alzheimer's disease, and 44 developed vascular dementia.
The researchers used Cox regression analyses, adjusting for age and
other covariates, to see if hormone levels were associated with risk of
developing dementia.
The report found that "Levels of bioavailable testosterone were not
associated with risk of cognitive decline and incident dementia. In
contrast, higher levels of bioavailable estradiol were associated with
an increased risk for cognitive decline and Alzheimer's disease." For
each standard deviation increase in estradiol level, the risk for the
disease went up by 25 percent. Furthermore, compared with the lowest
tertile of estradiol, men in the middle and highest tertile had .24 and
.28 points lower CASI scores, respectively, for each year increase in
age.
The researchers believe that the estradiol association could be
explained by increased aromatase activity in the brain which may be
associated with a neurodegenerative process. It is then possible that
the high levels of estradiol are a consequence or early marker of
Alzheimer's disease rather than a cause.
In conclusion, the authors report, "our findings of an increased risk of
cognitive decline and Alzheimer's disease associated with higher
estradiol are similar to recent findings in postmenopausal women.
Further studies are needed to examine whether there are mechanisms by
which estradiol may increase risk of cognitive decline and dementia."
Dan Wilson
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Books on the Mind
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