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DIABETES AS A RISK FACTOR FOR COGNITIVE DECLINE IN OLDER
PATIENTS
F. Limongi1, S. Maggi1, M. Noale1, G. Romanato1, P. Siviero1, G. Crepaldi1.
1
CNR, Institute of Neuroscience, Padova Section - Padova (Italy)
Objective: many studies support the hypothesis that diabetes is a risk factor for developing
cognitive decline and/or dementia. A systematic overview of prospective studies found that,
compared to people without diabetes, people with diabetes have a greater rate of decline in
cognitive function; a 1.5-fold greater risk of cognitive decline; and a 1.6-fold greater risk of
future dementia (Cukierman et al., 2005). In addition, the evolving concept that diabetes is a risk
factor for developing Alzheimer’s Disease is supported by scientific evidence and by the
common features of the two conditions, such as increased prevalence with aging, a genetic
predisposition, and comparable pathological features in the islet and brain.
Aim of our analyses is to assess the role of type 2 diabetes as a risk factor for cognitive
decline in males and females.
Method: analyses were based on the ILSA study (Italian Longitudinal Study on Aging) a
prospective, community-based cohort study, that included 5,632 individuals aged 65-84 years
of eight Italian municipalities with two follow-ups (1996; 2000). The cognitive assessment
included the administration of the Mini Mental State Examination, the Prose memory Test
and the Attention Matrix Test. Sex-specific analyses were carried out.
The association among diabetes and sociodemographic characteristics, lifestyle and main
diseases, separately for men and women, was assessed by the χ² test. As regards quantitative
variables, the difference between the mean values observed in the diabetic group versus the
non-diabetic group was evaluated by the general linear model (GLM) procedure. The mean
scores on the 3 tests, at baseline and follow-ups, were compared between diabetics and nondiabetics according to the GLM. Mean changes in each test, observed between baseline and
follow-ups, were assessed by a GLM corrected for scores obtained at baseline. At a
longitudinal level, the differences between scores obtained at baseline and follow-ups were
assessed separately for each test. Logistic regression models were then constructed, by sex, to
study the influence of diabetes and then of glycated hemoglobin (HbA1c) on cognitive
decline in the MMSE, Prose Memory Test and Matrix Test, at both follow-ups, adjusting for
other variables and baseline scores. Subjects with dementia at baseline were excluded from
the analysis. Results: At baseline, diabetic women had significantly worse scores on all
cognitive tests compared to non-diabetic women, but did not show worsening over time,
whereas men with diabetes did not show worse scores on cognitive tests at baseline compared
to nondiabetic males; however, diabetes in men was associated with a risk of cognitive
decline over time, particularly in attention. A poor glycaemic control (assessed by glycated
hemoglobin) was associated with poorer performance on Prose memory tests at follow-up in
both sexes. Discussion: The impact of diabetes on cognitive status might differ in older men
and women, probably because of a survival effect, with a higher mortality at a younger age
among diabetic men. The metabolic and cardiovascular abnormalities associated with diabetes
might be responsible for the cognitive decline, at different rates and ages, in men and women.
The association between a poor glycemic control and the risk of cognitive decline,
particularly in memory function is an extremely important fact, since impairment in even a
single domain may favour progressive and overall decline in cognitive capacities. However,
literature data regarding the effect of glycemic control on cognitive function are still
controversial. A routine assessment of diabetes complications in the elderly should include
cognitive evaluation in both sexes.