Cognitive decline and dementia in diabetes—systematic overview of prospective observational studies

Abstract

Aims/hypothesis: We systematically reviewed and summarised prospective data relating diabetes status to changes in cognitive function over time. Methods: Published reports of longitudinal studies that described assessment of cognitive function in people with diabetes were sought. Studies were included if they assessed cognitive function in participants with diabetes at the beginning and at follow-up. Studies were excluded if they had (1) a follow-up period of less than 1 year, (2) a rate of loss to followup in excess of 30%, or (3) described selected subgroups. Change in cognitive function was recorded as either the mean change in score and/or the proportion of individuals developing various degrees of change in cognitive function. A pooled estimate was calculated for the latter. Results: Of 1,165 abstracts and titles initially identified, 25 articles met the inclusion and exclusion criteria. Individuals with diabetes had a 1.2-to 1.5-fold greater change over time in measures of cognitive function than those without diabetes. When assessed by the Mini-Mental State Exam and the Digit Symbol Span tests, a diagnosis of diabetes increased the odds of cognitive decline 1.2-fold (95% CI 1.05-1.4) and 1.7-fold (95% CI 1.3-2.3), respectively. The odds of future dementia increased 1.6-fold (95% CI 1.4-1.8). Conclusions/ interpretation: Compared to people without diabetes, people with diabetes have a greater rate of decline in cognitive function and a greater risk of cognitive decline. Cognitive dysfunction should therefore be added to the list of chronic complications of diabetes.

Presence of the APOE ε4 allele modifies the relationship between type 2 diabetes and cognitive performance: the Maine–Syracuse Study

“…Diabetes mellitus has been associated with decrements in cognitive performance and dementia in cross-sectional and longitudinal studies [1][2][3][4]. A recent review indicates that individuals with diabetes have a greater risk of cognitive decline and a greater risk of developing dementia than do non-diabetic individuals [3].…”

“…A recent review indicates that individuals with diabetes have a greater risk of cognitive decline and a greater risk of developing dementia than do non-diabetic individuals [3]. Among others, possible mechanisms for this association include oxidative stress, accelerated ischaemic brain damage [5] and impaired use of glucose during cognitive tasks [6].…”

Severe hypoglycaemia and cognitive impairment in older patients with diabetes: the Fremantle Diabetes Study

“…There are few detailed prospective studies of hypoglycaemia and cognition in older patients [3,11]. We have previously observed cross-sectional associations between self-reported severe hypoglycaemia and cognitive impairment in an elderly sample of patients with type 2 diabetes [13].…”

“…This latter group has an increased risk of cognitive impairment [3], which may be associated with insulin therapy [4,5]. Since the association between diabetes and cognitive impairment appears confined to middle-aged or older individuals [6], the ageing brain could be particularly susceptible to neuroglycopenia.…”

A randomised trial comparing low-fat diets differing in carbohydrate and protein ratio, combined with regular moderate intensity exercise, on glycaemic control, cardiometabolic risk factors, food cravings, cognitive function and psychological wellbeing in adults with type 2 diabetes: Study protocol

“…Furthermore, previous studies have indicated that individuals with T2DM have a greater rate and risk of cognitive decline compared with controls without T2DM and a higher risk of dementia [4]. The cognitive domains affected are processing speed; attention; verbal and visual memory; psychomotor performance/coordination and executive function [5][6][7][8].…”