BACKGROUND:

Type 2 diabetes is associated with dementia risk, but evidence is limited for possible associations of diabetes and prediabetes with cognitive decline.

OBJECTIVE:

To determine whether diabetes in midlife is associated with 20-year cognitive decline and to characterize long-term cognitive decline across clinical categories of hemoglobin A1c (HbA1c) levels.

DESIGN:

Prospective cohort study.

SETTING:

The community-based ARIC (Atherosclerosis Risk in Communities) study.

PARTICIPANTS:

13,351 black and white adults aged 48 to 67 years at baseline (1990 to 1992).

MEASUREMENTS:

Diabetes was defined by self-reported physician diagnosis or medication use or HbA1c level of 6.5% or greater. Undiagnosed diabetes, prediabetes, and glucose control in persons with diagnosed diabetes were defined by clinical categories of HbA1c level. Delayed word recall, digit symbol substitution, and word fluency tests were used to assess cognitive performance and were summarized with a global Z score.

RESULTS:

Diabetes in midlife was associated with a 19% greater cognitive decline over 20 years (adjusted global Z-score difference, -0.15 [;95% CI, -0.22 to -0.08];) compared with no diabetes. Cognitive decline was significantly greater among persons with prediabetes (HbA1c level of 5.7% to 6.4%) than among those with an HbA1c level less than 5.7%. Participants with poorly controlled diabetes (HbA1c level ≥ 7.0%) had greater decline than those whose diabetes was controlled (adjusted global Z-score difference, -0.16; P = 0.071). Longer-duration diabetes was also associated with greater late-life cognitive decline (P for trend < 0.001). Rates of decline did not differ significantly between white and black persons (P for interaction = 0.44).

LIMITATION:

Single HbA1c measurement at baseline, 1 test per cognitive domain, and potential geographic confounding of race comparisons.

CONCLUSION:

Diabetes prevention and glucose control in midlife may protect against late-life cognitive decline.

PRIMARY FUNDING SOURCE:

National Institutes of Health.

PMID:

 

25437406

 

[PubMed – indexed for MEDLINE] 

PMCID:

 

PMC4432464

 

Free PMC Article

Type 2 diabetes mellitus (T2DM) is a risk factor of dementia. The effect of T2DM treatment quality on dementia risk, however, is unclear. 1,342 elderly individuals recruited via general practitioner registries (AgeCoDe cohort) were analyzed. This study analyzed the association between HbA1c level and the incidence of all-cause dementia (ACD) and of Alzheimer’s disease dementia (referred to here as AD). HbA1c levels ≥6.5% were associated with 2.8-fold increased risk of incident ACD (p = 0.027) and for AD (p = 0.047). HbA1c levels ≥7% were associated with a five-fold increased risk of incident ACD (p = 0.001) and 4.7-fold increased risk of incident AD (p = 0.004). The T2DM diagnosis per se did not increase the risk of either ACD or AD. Higher levels of HbA1c are associated with increased risk of ACD and AD in an elderly population. T2DM diagnosis was not associated with increased risk if HbA1c levels were below 7%.

PMID:

 

25524954

 

[PubMed – in process]

OBJECTIVE:

Memory has been examined in subjects with imaging markers of cerebrovascular disease, but learning has been less well studied. We examined the relationship among subclinical cerebrovascular disease, cerebral volumes, and verbal learning in an ethnically and racially diverse community sample.

METHODS:

A clinically stroke-free subset of Northern Manhattan Study participants underwent cognitive testing and brain MRI with quantification of white matter hyperintensity volume (WMHV) and total cerebral volume (TCV) using semiautomated segmentation. We used generalized linear regression and mixed models to examine the association between imaging findings and verbal learning.

RESULTS:

There were 1,272 participants (61% women, mean age 70 ± 9 years). Participants with greater WMHV and smaller TCV remembered fewer total words on a list-learning task (β = -0.83 per SD change in WMHV, 95% confidence interval [CI] = -1.22 to -0.45, p < 0.0001; and β = 0.48 per SD change in TCV, 95% CI = 0.05 to 0.90, p = 0.03, respectively). Subclinical brain infarction (SBI) was not associated with total words learned (β = -0.04, 95% CI = -1.08 to 1.00, p = 0.94). Those with greater WMHV had increased odds of a flatter learning slope. After excluding participants with SBI, the association between total words learned and WMHV remained significant. All measurements were adjusted for age, education, race/ethnicity, medical insurance status, and the presence of SBI.

CONCLUSIONS:

White matter hyperintensities, a marker of cerebral small vessel disease, may have an impact on learning slope. This suggests that verbal learning performance can be incorporated into neuropsychological measures for vascular cognitive impairment and that cerebrovascular disease discovered on imaging affects the ability to learn new information.

© 2015 American Academy of Neurology.

PMID:

 

26002489

 

[PubMed – as supplied by publisher]