Use it or lose it has become
something of a byline for Alzheimer's research lately.
It has been evident for some years that an underused brain
is at greater risk of cognitive decline in old age. There's
no longer any doubt that people who progress further in
their education are less likely to develop Alzheimer's
disease(AD). Now, a study in the August 10 issue of Neurology
found that mentally demanding jobs also seem to offer
a protective effect.
Researchers from the Case Western
Reserve University School of Medicine interviewed 122
AD patients and 235 healthy age-matched controls on
their employment history during their 20s, 30s, 40s
and 50s. Using the US Labour Department job rankings,
the researchers compared the mental and physical challenges
placed on the workers. The results were adjusted for
age, sex, race and education.
There was little difference between
the jobs Alzheimer's patients had held in their 20s
and those held by healthy subjects at the outset of
their careers. But over the succeeding decades, the
career paths of the two groups diverged. People who
later developed Alzheimer's tended to remain in jobs
of about the same level of mental difficulty as those
they held in their 20s. The healthy controls were more
likely to have been promoted or to have moved to a harder
job. Overall, by Labour Department rankings, the complexity
of their work grew by about 33% over the course of four
decades, while the complexity of work performed by the
AD patients remained about the same.
Since these results held up whether
the researchers controlled for education or not, they
suggested that honing mental acuity through a challenging
work environment is somehow protective against AD. "It
could be that higher levels of mental demands result
in increased brain cell activity, which may help maintain
a 'reserve' of brain cells that resists the effects
of Alzheimer's," said lead author, Kathleen Smyth, PhD.
On the other hand, "It could be that the disease has
a very early effect on the individual's capacity to
pursue a mentally challenging occupation." That is an
alarming hypothesis, since it would mean that patients
who go on to develop AD actually suffered cognitive
deficits in mid-life.
One other factor could be in play
that the researchers were unable to control for. People
with more demanding jobs don't merely tend to be better
educated, they also tend to be richer. "People with
higher socioeconomic status generally hold jobs with
higher mental demands compared to those with lower socioeconomic
status," said Dr Smyth. "Therefore, variations in income,
access to healthcare, better nutrition and other factors
related to socioeconomic status could be responsible
in part for our findings."
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