Abstract
Background:
Long term diabetes is associated with cognitive decline. Blood glucose control improves outcomes in patients with diabetes, it is unclear if intensive glucose control prevents cognitive decline. The aim of this study is to conduct a meta-analysis to determine the effects of intensive glucose control on cognitive decline in patients with diabetes.
Methods:
We searched the MEDLINE database (1966 to December 2013) and supplemented the search with manual searches of bibliographies of key relevant articles. Keywords used for the search were: diabetes mellitus, cognitive decline, cognitive function, cognitive impairment, and glucose control. We selected all randomized studies where a measurement of cognitive decline and the level of glucose control were reported in patients with diabetes. We calculated the weighted standardized mean difference (SMD) of the measurement of cognitive decline between the intensive and standard glucose control arm. We also conducted meta-regression to evaluate the effect of the type of diabetes had on the results and stratified the analysis by type of diabetes.
Results:
The search strategy yielded 260 studies, of which only 7 met our eligibility criteria. Only three studies included subjects with type 2 diabetes, patients with type 2 diabetes had a median age of 62(59-63), 48(42-60) were female, the median HbA1c was 8% and the median duration of diabetes was 9 years. We included four studies with type 1 diabetes with a median age of 27(16-29) years, 49(49-50) % were female, the median Hba1c was 9% and the median duration of diabetes was 6(5-18) years. The weighted SMD of each cognitive test is shown in Table 1.
Conclusions:
Intensive glucose control prevents cognitive decline. The largest improvements were seen in the memory and speed processing domains. This was seen mostly in middle-aged type 2 diabetics with diabetes for 9 years and slightly out of control HbA1c.