PracticeUpdate: Diabetes

EDITOR’S PICKS 11

Cognitive Function Deficits AssociatedWith Long-Duration Type 1 Diabetes and Vascular Complications Diabetes Care Take-home message • In this study, 82 individuals with at least 50 years of T1D, 31 age-matched participants with T2D, and 30 age-matched participants without diabetes were included to assess complications with cognition. Worse performance on immediate and delayed recall was reported in patients with T1D and T2D compared with controls. Additionally, patients with T1D and T2D had significantly worse psychomotor speed in both hands and a trend toward worse executive function compared with controls. Cardiovascular disease was associated with worse executive function, and proliferative diabetic retinopathy was associated with slower psychomotor speed in individuals with at least 50 years of T1D. • These findings demonstrate the importance of cognitive evaluation and implementation of behavior modification in patients with T1D. Abstract

COMMENT By Naomi Sage Chaytor PhD, ABPP

OBJECTIVE Patients with type 1 diabetes now live long enough to experience cognitive decline. During middle age, they show mild cognitive deficits, but it is unknown whether severity increases with aging or whether cognitive pro- files are similar to those of age-matched peers with and without diabetes. RESEARCH DESIGN AND METHODS We tested and compared cognition in 82 individuals with 50 or more years of type 1 diabetes (Medalists), 31 age- matched individuals with type 2 diabetes, and 30 age-matched control subjects without diabe- tes. Medical histories and biospecimens were collected. We also evaluated the association of complications with cognition in Medalists only. RESULTS Compared with control subjects, both individuals with type 1 diabetes and individu- als with type 2 diabetes performed worse on immediate and delayed recall (P ≤ 0.002) and psychomotor speed in both hands (P ≤ 0.01) and showed a trend toward worse executive function (P = 0.05). In Medalists, cardiovascular disease was associated with decreased executive func- tion and proliferative diabetic retinopathy with slower psychomotor speed. CONCLUSIONS Both patients with type 1 and patients with type 2 diabetes showed overall worse cognition than control subjects. Further, in Medalists, a relationship between complications and cognition was seen. Although both groups with diabetes showed similar deficit patterns, the underlying mechanisms may be different. Now that patients with type 1 diabetes are liv- ing longer, efforts should be made to evaluate cognition and to identify modifying behaviors to slow decline. Cognitive Function Deficits Associated With Long-Duration Type 1 Diabetes and Vascu- lar Complications. Diabetes Care 2018 Jun 05;[EPub Ahead of Print], G Musen, LJ Tinsley, KA Marcinkowski, et al. www.practiceupdate.com/c/69353

A lthough type 2 diabetes has become an established risk factor for cognitive decline and dementia, the impact of type 1 diabetes on cognitive functioning is less clear. This is particularly true in older adults, who may have had type 1 diabetes for most of their lives and who have a higher burden of diabetes-related complications that carry additional cognitive risk. The recent case-control study by Musen and colleagues published in Diabetes Care characterizes the cognitive status of adults who have had type 1 diabetes for over 50 years. They compared 82 “50- year Medalists” with 31 age-matched adults with type 2 diabetes and 30 age-matched adults without diabetes. This study adds to a nascent literature on cognition in older adults with type 1 diabetes. There are, however, features of the study design that limit the conclusions that can be drawn. First, although the authors matched the groups on age, they were not matched on education, which is an important determinant of cognitive performance. Furthermore, all groups had intelligence scores that were well above average for the general population, with the normal control group scoring the highest (in the superior range). Although IQ was controlled for statistically in some analyses, the groups are likely different in other important respects. For example, there may be an interaction between IQ and vulnerability to the cognitive effects of diabetes, as it is well known that “cognitive reserve” is an important buffer to decline secondary to aging and dementia. Consistent with this, the type 1 diabetes cohort produced scores that were well within normal limits across all measures, despite being statistically lower than the controls’ above-average memory test scores. Although there were likely some individuals who had clinically meaningful cognitive impairment, this was not reported in the manuscript. This tempers the authors’ conclusion that those with long-duration diabetes have cognitive function deficits. Lastly, comparisons between the two dia- betes groups, which generally found no differences, were confounded by duration of diabetes (19 vs 55 years). These limitations aside, perhaps the most important take- away from this paper is how well this select group is doing, particularly those who have avoided diabetes-related complications. It remains to be seen if this will be rep- resentative of most people with type 1 diabetes as they age.

Dr. Chaytor is a Board-Certified Clinical Neuropsychologist and Associate Professor in the Elson S. Floyd College of Medicine at Washington State University in Spokane, Washington.

VOL. 2 • NO. 3 • 2018