Table 2.
Studies investigating the role of diabetes in cognitive impairment.
| Study author & yr | Participants | Duration | Cognitive tests | Main findings |
|---|---|---|---|---|
| Palta P. et al (2017) | 3069 adults aged 72–96 yr | Median follow-up of 6.1 yr | Memory, visuo-spatial construction, language, psychomotor speed, executive function | Older adults with diabetes exhibited greater baseline differences in executive function and greater declines in language. No significant differences in the rate of cognitive decline in composite cognitive domain scores. |
| Mallorquí-Bagué N. et al (2018) | 6823 older individuals with overweight/obesity and metabolic syndrome | Cross-sectional analysis | Executive function and BMI were negatively associated with type 2 diabetes. Participants with type 2 diabetes and better glycemic control displayed better cognitive performance. | Type 2 diabetes was associated with worse executive function, and BMI had a negative effect on executive function. |
| Jacobson A.M. et al (2021) | 1051 participants with type 1 diabetes | 32 yr of follow-up | Memory, psychomotor and mental efficiency | Cognitive performance declined over 32 yr of follow-up. Higher HbA1c levels, severe hypoglycemia, and elevated systolic blood pressure were associated with greater cognitive decline. |
| Lehtisalo J. et al (2016) | 364 participants with impaired glucose tolerance | Intervention period 4 yr | Cognitive assessment (CERAD test battery, Trail Making Test A) | Better glycemic control predicted better cognitive performance 9 yr later. Learning effects in cognitive testing were not evident in people with long diabetes duration. |
| Lutski M. et al (2017) | 489 patients with cardiovascular disease | 2 decades of follow-up | Cognitive function assessment | Insulin resistance was related to poorer cognitive performance and greater cognitive decline among patients with cardiovascular disease. |
| Hayden K.M. et al (2021) | 3938 participants with type 2 diabetes | Up to 18 yr of follow-up | Cognitive function assessment | Intensive lifestyle intervention did not result in preserved cognitive function or slower rates of cognitive decline. |
| Espeland M.A. et al (2018) | 3802 individuals with type 2 diabetes | 10–13 yr of follow-up | Cognitive impairment assessment | Cognitive impairment prevalence was lower in women than in men among overweight and obese adults with type 2 diabetes. |
| Williamson J.D. et al (2014) | 2977 participants with type 2 diabetes | 40 mo of follow-up | Cognitive function and total brain volume assessment | Intensive blood pressure control was associated with greater decline in total brain volume. |
| An K. et al (2021) | 235 Patients with type 2 diabetes | Cognitive assessment | Verbal disfluency and cognitive performance | Decreased plasma level of lipoprotein lipase predicted early cognitive deficits. |
| Furlano J.A. et al (2023) | 124 60–80 yr old with prediabetes or overweight/obesity | 6 mo of resistance training | Cognitive ability assessment, functional MRI | Resistance training improved cognitive ability and functional MRI patterns. |
| Emanuel A.L. et al (2019) | 25 type 1 diabetes patients with retinopathy | Longitudinal study | Cognitive performance, cerebral blood flow (CBF) | Lower cognitive performance was associated with white matter lesions and lower skin capillary perfusion in type 1 diabetes patients. |
| Cukierman-Yaffe T. et al (2015) | 31,227 participants with diabetes | Median follow-up of 4.7 yr | Relationship between fasting plasma glucose values and dementia, cognitive decline, and cognitive impairment | Higher fasting plasma glucose values were associated with an increased risk of dementia, cognitive decline, and cognitive impairment in people with diabetes. |
| Lotan R. et al (2021) | 544 Older adults with type 2 diabetes | 6 mo of dietary AGEs reduction | Cognitive performance, olfactory function, odor-induced brain alterations | Dietary AGEs reduction improved cognition and olfactory function in obese individuals with type 2 diabetes. |
| Zhang Z. et al (2019) | 800 Obese and nonobese people with type 2 diabetes | Cross-sectional and 3-mo intervention | Cognitive functioning, olfactory function, brain activation | Obese individuals with type 2 diabetes had worse cognitive function and olfactory function, which improved with weight loss and improved glycemic control. |
| Spauwen P.J.J., et al (2013) | 704 participants with type 2 diabetes | 5 yr of follow-up | Cognitive function assessment | Presence of cerebral small vessel disease was associated with cognitive decline in type 2 diabetes. |
| Zheng F., Yan L., Yang Z. et al (2018) | 5189 | 10 yr | Global cognitive z scores, memory z scores, executive function z scores | - 1 mmol/mol increment in HbA1c associated with cognitive decline < br> - Prediabetes and diabetes linked to increased cognitive decline |
| Botond Antal et al (2022) | 20,314 | Not specified | Not specified | - T2DM associated with cognitive deficits, especially executive function < br> - Gray matter atrophy in T2DM < br> - Metformin didn’t improve outcomes |
| Moran C. et al (2019) | 705 | 4.6 yr | Verbal memory, cortical thickness | - T2DM associated with decline in verbal memory and fluency < br> - T2DM linked to lower baseline cortical thickness |
| Xie K. et al (2022) | 732 | 5–8 yr | COGTEL scores, memory, working memory | - Lower cognitive performance in T2DM < br> - Memory-related domains sensitive to T2DM |
| Callisaya M.L. et al (2019) | Not specified | 5 yr | Cortical thickness, cognitive function | - T2DM associated with cognitive decline via neurodegeneration |
| Varghese S.M. et al (2022) | 800 | Not specified | Addenbrooke Cognitive Examination-III | - Cognitive impairment in 63.8% of diabetics < br> - Memory-related domains affected |
| Rawlings A.M. et al (2014) | 13,351 | 20 yr | Cognitive function | - Diabetes linked to greater cognitive decline < br> - Prediabetes associated with cognitive decline |
| Lalithambika C.V. et al (2019) | 70 | Not specified | Montreal Cognitive Assessment (MoCA) | - High prevalence of MCI in type 2 diabetic patients < br> - Poor glucose control correlated with cognitive impairment |
| Bashir J. et al (2022) | 61 | Not specified | Montreal Cognitive Assessment test (MoCA) | - MCI common in advanced T2DM < br> - Hyperinsulinaemia correlated with MCI |
| Crane P.K. et al (2013) | 2067 | 6.8 yr | Clinical measurements of glucose levels | - Higher glucose levels associated with increased dementia risk in non-diabetic and diabetic individuals |
| Hazari M.A.H. et al (2015) | 46 | Not specified | P300 event-related potentials (ERPs) | - Cognitive dysfunction in T2DM, more pronounced with longer disease duration < br> - Hypertension worsened cognitive function |
AGEs = advanced glycation end products.