Longitudinal Associations of Newly Diagnosed Prediabetes and Diabetes with Cognitive Function among Chinese Adults Aged 45 Years and Older

Association of prediabetes progression and regression with cognitive decline: Findings from the CHARLS

AIM

The aim of the study was to describe the association of prediabetes progression and regression with change in cognitive function.

METHODS

Data from three waves (2011, 2015 and 2018) of the China Health and Retirement Longitudinal Study (CHARLS) were analysed. Diabetic statuses in 2011 and 2015 were ascertained using the American Diabetes Association criteria. Cognitive function was assessed and standardized at all three waves, where a total score and its two components (episodic memory and metal status) were calculated. We evaluated the association of prediabetes progression and regression (from 2011 to 2015) with changes in cognitive function from 2011 to 2015 and from 2015 to 2018.

RESULTS

Of 2590 participants (56% women, mean age 58.6 ± 8.4 years) with prediabetes, 12% progressed to diabetes and 41% regressed to normoglycaemia. Compared with participants who remained as prediabetes, those who progressed to diabetes showed a trend to have accelerated decline in episodic memory (β = -0.11, 95% confidence interval -0.22 to 0.003, p = 0.057). However, participants who regressed to normoglycaemia did not have less cognitive decline. Neither prediabetes progression nor regression predicted change in cognitive function from 2015 to 2018. In a separate group of participants who remained as normoglycaemia (n = 858), changes in cognitive function from 2011 to 2015 and from 2015 to 2018 were similar to those who remained as prediabetes.

CONCLUSION

In people with prediabetes, progression to diabetes may be associated with accelerated cognitive decline but regression to normoglycaemia does not retard cognitive decline. Prediabetes progression and regression may not be predictive of change in cognitive function.

Cognition and BDNF levels in prediabetes and diabetes: A mediation analysis of a cross-sectional study

AIM

Clinical and epidemiological studies suggest links between dementias and Type 2 diabetes (T2DM). The underlying mechanisms of diabetes-related cognitive impairment are largely unknown. This study aims to investigate the role of BDNF in cognitive impairment in prediabetes and T2DM.

METHODS

The study included 68 patients with prediabetes (preDM), 96 patients with T2DM, and 65 healthy controls. The cognitive function of the patients was evaluated with the Montreal Cognitive Assessment (MoCA) test and serum BDNF levels were measured by Elisa. The MoCA scores and BDNF levels were compared between diabetes groups after adjusting for age, gender, and education using ANCOVA. The role of BDNF in the diabetes-related cognitive impairment was investigated through mediation analysis.

RESULTS

Patients with T2DM had significantly lower cognitive performance, particularly in memory. Diabetes was found to be a predictor of both cognitive impairment and BDNF levels. A significant increase in serum BDNF levels was observed in patients with T2DM. However, the mediator role of BDNF in the pathology of cognitive impairment in diabetes was not determined.

CONCLUSION

Cognitive impairment is prevalent in patients with T2DM and should be included in routine screening for complications. The results of the mediation analysis suggest that although BDNF is a biomarker affected by T2DM and cognition, it does not play a mediator role between cognitive impairment and diabetes.