Cognitive function in diabetic persons with peripheral neuropathy: a systematic review and meta-analysis

ABSTRACT

Objectives

The aim of this study is to improve our knowledge of cognitive function in individuals with type 1 (T1DM) or type 2 (T2DM) diabetes mellitus and with peripheral diabetic neuropathy (DPN).

Methods

A systematic review and meta-analysis was performed of publications included in PubMed, Scopus, PsycInfo and Web of Science databases until November 2021. The study was registered in PROSPERO (CRD42021229163).

Results

A total of 832 articles were identified, 19 of which were selected. The presence of DPN was associated with global cognitive impairment in the T1DM persons in two studies (p=0.046;p=0.03)    and T2DM persons in four (p<0.00;p<0.02;p=0.011;p≤0.05)     . Differences in specific dimensions – memory, attention, and psychomotor speed – were found in both kinds of diabetes. The meta-analysis showed that the individuals with T2DM and DPN presented a lower mean cognitive performance than those without DPN (-1.0448;95%CI:-1.93%;-0.16%). Depression was associated with impaired cognitive function in these diabetic persons (p < 0.01).

Conclusion

The review reveals the great variability in instruments and methodologies, while providing results that support the presence of both global and domain-specific cognitive impairment in diabetic persons with DPN.

KEYWORDS:

• Diabetes mellitus
• cognitive function
• meta-analysis
• peripheral diabetic neuropathy
• systematic review

Article highlights

• Diabetes mellitus (DM) has been associated with a decrease in cognitive function. Peripheral neuropathy (PN) is a common complication of DM that can produce structural alterations in the brain. However, its relationship with cognitive function has been the subject of little research.

• This review aims to analyze cognitive function in persons with type 1 diabetes mellitus (T1DM) or type 2 diabetes mellitus (T2DM) with peripheral neuropathy diabetic (DPN).

• A systematic review of the publications included in the PubMed, Scopus, PsycInfo and Web of Science databases was conducted until November 2021 and a meta-analysis was performed to synthesize the results obtained. Original articles with a transversal and longitudinal design published in English or Spanish were included.

• The search identified a total of 832 potential articles and 19 articles fulfilled the inclusion criteria.

• The presence of DPN was associated with overall cognitive impairment in both T1DM and T2DM persons. Furthermore, persons with T1DM and DPN presented impairment in attention/concentration, mental flexibility and psychomotor speed. The dimensions affected in persons with T2DM and DPN were: executive function, memory and reaction time.

• Meta-analysis showed that persons with DMT2 and DPN had worse cognitive performance than those with DMT2 without DPN.

• A depressed mood was associated with worse cognitive performance in persons with DPN.

• The review shows considerable variability in the instruments and methodologies used in the studies, although it provides results that support the presence of cognitive impairment in diabetic persons with DPN, both on a global level and on the level of specific dimensions.

Acknowledgments

The authors would like to thank the University of Cádiz for providing the access to the scientific literature, and to the native English speaker that helped to translate the manuscript.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or conflict with the subject matter or materials discussed in this manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Supplementary material

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Additional information

Funding

This paper was not funded.