June 25, 2015
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Diabetes-cognitive decline risk similar for US, Chinese adults

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Both U.S. and Chinese older adults with type 2 diabetes showed cognitive decline, particularly in executive function tests, when compared with adults who did not have diabetes, according to research in the Journal of Alzheimer’s Disease.

In a comparative analysis of two ongoing population-based studies examining cognition in older adults from the United States and China, researchers found that participants with type 2 diabetes in both countries performed significantly worse on cognitive tests, including tests that called for problem solving and decision making.

“We wanted to study diabetes and cognitive impairment in these two completely different ethnic groups to see whether there are any differences,” Rosebud Roberts, MB, ChB, an epidemiologist at the Mayo Clinic, said in a press release.

Roberts, Qianhua Zhao, MD, PhD, of Fudan University and Huashan Hospital in Shanghai, China, and colleagues analyzed data from 3,348 adults aged 50 years or older (mean age, 68 years) without dementia participating in the Shanghai Aging Study (SAS), as well as 3,734 adults aged 50 years or older (mean age, 76 years) without dementia participating in the Mayo Clinic Study of Aging (MCSA). In both studies, participants completed a comprehensive neuropsychological evaluation to assess performance in memory, executive function, language and visuospatial skills; researchers with the SAS adapted Western tests to harmonize with Chinese culture. Researchers used medical records to determine whether participants had type 2 diabetes and performed domain-specific cognition analyses.

Researchers found that participants with type 2 diabetes performed significantly worse in all cognitive tasks compared with participants who did not have diabetes. In particular, type 2 diabetes was associated with worse performance in executive function — including reasoning, mental flexibility, problem solving and decision making — in both the SAS (P = .001) and MCSA studies (P = .008) in the total sample and in a cognitively normal sub-sample.

Researchers also linked type 2 diabetes with poor performance in visuospatial skills, language and memory in the SAS study, but not in the MCSA study. Researchers noted that the SAS study population developed diabetes at an earlier age compared with the MCSA population, possibly explaining the difference.

In a press release, Roberts said the research shows that cognitive impairment may be an early effect of diabetes, and that diagnosis of diabetes at an earlier age results in greater cognitive deficits.

“This study supports the hypothesis that older adults with [diabetes] have reduced cognitive function, especially in the executive function domain, and this finding is consistent in both Chinese and Americans with northern European ancestry regardless of the different age and vascular burdens,” the researchers wrote. “Prospective studies on the longitudinal outcomes of [diabetes] in non-demented persons are underway to further elucidate the clinical relevance and implications of [diabetes]-associated cognitive dysfunction in the community setting.” by Regina Schaffer

Disclosure: Roberts and Zhao report no relevant financial disclosures. Please see the full study for other authors’ relevant financial disclosures.