Evaluating thinking and reasoning performance in adults with type 1 diabetes over the long-term

This long-term study looked at mental sharpness and coordination as adults age with type 1 diabetes (T1D). It found that blood sugar control over the previous 30 years influences later coordination and memory.

People with type 1 diabetes (T1D) are now living much longer and fuller lives, due to improved treatment. Because of this, aging gracefully with T1D is becoming more of a concern.

The bodies of people with T1D cannot create the hormone insulin, which is responsible for controlling the amount of glucose (sugar) in the blood. Over time, high blood glucose can damage delicate tissues and blood vessels. People with T1D use synthetic insulin to control their blood glucose levels. However, it can be difficult to time insulin precisely in order to avoid both high blood glucose and hypoglycemia (abnormally low glucose).

Over time, both high blood glucose and hypoglycemia can damage delicate blood vessels and tissues. This includes damage to the small vessels which supply blood to the brain. People with T1D are more likely to develop memory and other cognitive (thinking and reasoning capacities) impairments as they become older. These long-term effects are still being studied.

This study included 1051 participants with T1D. Participants were between 13 and 39 years when they enrolled, and between 43 and 75 years by the end of the study. Glycated hemoglobin (HbA1c), which indicates blood glucose control over the previous 2 – 3 months, was measured repeatedly. The participants were also tested for other factors such as blood pressure, kidney function, and eye health. Tests of memory and cognitive function were given after 2, 5, 18, and 32 years.

Patients’ average mental function improved from the beginning of the study to 5 years later. However, average coordination was lower by 18 years after the start of the study. Coordination decreased notably by the end of the study. Memory also decreased by the end of the study.

Glycated hemoglobin (HbA1c) is an estimate of glucose levels over the previous 2 – 3 months. Higher values can indicate poorly controlled high blood glucose. Patients with higher HbA1c over the previous 30 years had worse coordination. Patients with high blood pressure or who reported at least 1 serious hypoglycemia event also had worse coordination. Poor glucose control, episodes of hypoglycemia, and high blood pressure were related to mental aging. Having all three of these factors was equivalent to 9.4 years of premature aging. On the other hand, the patients with the best glucose control did not experience any declines in coordination or memory over the course of the study.

The researchers compared how having certain health conditions affected memory and coordination, after adjusting for other factors. The statistical value Beta (β) measures this relationship, with more negative values indicating a stronger decrease in coordination. Nerve damage and heart disease were related to lower coordination. Both memory and coordination were lower for patients with kidney disease. The eye condition macular edema was strongly related to lower coordination. 

This study found that glucose control, blood pressure, and diabetes complications can influence long-term memory and coordination for patients with T1D. The patients with the best glucose control stayed mentally sharp over the course of the 30-year study.

The patients’ outcomes may have been influenced by other factors, such as socioeconomic income.

Talk to your doctor about your long-term health goals and how your diabetes management now can influence them.