Minn. — Diabetes is a known risk factor for cognitive
decline and dementia, age-related conditions that affect
memory and thinking skills. However, little is known about how
the diabetes-cognitive decline link compares across cultures.
from Mayo Clinic and Huashan Hospital in Shanghai explored the
association between Type 2 diabetes and cognitive impairment
to find out if the relationship varies in different
populations. Study participants had not been diagnosed with
memory-related diseases, such as vascular dementia or
study, the researchers evaluated data from two large, ongoing,
population-based studies: the Shanghai Aging Study (SAS) and
the Mayo Clinic Study of Aging (MCSA). Both use similar
designs and methodologies. For example, both studies recruit
participants from a defined population; include an on-site,
in-person evaluation; use similar or comparable tests of
cognition, and include participants over age 50. The SAS uses
neuropsychological tests adapted from Western tests to
harmonize with Chinese culture.
scientists analyzed medical data from 3,348 Chinese adults and
3,734 American adults, all of whom had undergone cognitive
testing and were dementia-free. Participants' medical records
were used to determine whether they had Type 2 diabetes.
researchers found that all of the participants who had Type 2
diabetes, regardless of their population study, performed
significantly worse on cognitive tests, compared to
participants who did not have diabetes. These findings suggest
that diabetes is linked to cognitive impairment in both
Eastern and Western cultures.
wanted to study diabetes and cognitive impairment in these two
completely different ethnic groups to see whether there are
any differences. We found that in both cohorts, having a
history of diabetes was associated with greater impairment in
cognitive function," says study co-author Rosebud
Roberts, an epidemiologist at Mayo Clinic.
results were the same — even after adjusting for age, gender
and education, as well as vascular problems. More
specifically, the American and Chinese study participants with
diabetes performed considerably worse on executive function
tests, compared to people in both study populations who did
not have diabetes. Executive function is the ability to make
decisions, plan and problem-solve, and is associated with the
frontal lobe of the brain.
Shanghai population, a diabetes diagnosis also was associated
with poorer performance on tests of memory, visual-spatial
skills and language. One possible reason for this difference
is that the population studied by the SAS developed diabetes
at an earlier age, compared to the MCSA population.
Roberts says the research is important, because it shows that
impairment in executive function may be an early effect of
diabetes, and earlier age at diabetes diagnosis results in
greater cognitive deficits. However, she adds, the overall
effects of diabetes on cognition are similar in Western and