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Prolonged, high HbA1c may increase dementia risk in type 1 diabetes

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September 7, 2018

Older adults with type 1 diabetes with prolonged exposure to HbA1c at least 8% are at least twice as likely to develop dementia over 6 years vs. similar adults with only 10% of measurements in the same range, according to findings published in Diabetes Care.

Mary E. Lacy

“In this study of older adults with type 1 diabetes, we found a significant association between glycemic control and dementia,” Mary E. Lacy, PhD, postdoctoral fellow in the department of epidemiology and biostatistics at University of California San Francisco, told Endocrine Today. People with a majority of HbA1c measurements above 8% and 9% were 65% and 79% more likely to be diagnosed with dementia, respectively, compared with those with fewer than 50% of their HbA1c measurements exposed to these ranges. Conversely, those with a majority of their HbA1c measurements between 6% and 6.9% and 7% and 7.9% were 45% less likely to be diagnosed with dementia. These findings suggest that effective glycemic control could be an important tool for reducing dementia risk in this population.”

Lacy and colleagues analyzed electronic medical records from 3,433 adults aged at least 50 years with type 1 diabetes and no prevalent dementia at baseline from the Kaiser Permanente Northern California Diabetes Registry, a registry of all members with diabetes using a combination of pharmacy and laboratory information, hospitalization records and outpatient diagnoses. Cohort entry date was defined as the first date between 1996 and Sept. 30, 2015, that a patient was aged at least 50 years and had a type 1 diabetes diagnosis (mean baseline age, 56 years; 80.1% white; 47.1% women). Dementia diagnoses were identified based on EMRs, and HbA1c measurements were obtained from the Kaiser laboratory database (mean number of measurements per patient, 13.5). Patients were stratified by HbA1c level into the following categories: less than 6%; 6% to 6.9%; 7% to 7.9%; 8% to 8.9%; and at least 9%. Researchers used Cox proportional hazard models to estimate the association between categories of cumulative exposure to HbA1c and risk for dementia, with age used as the time scale.

During a mean follow-up of 6.3 years, 155 adults (4.5%) were diagnosed with dementia, with a mean age at diagnosis of 64 years.

Researchers found that dementia risk was higher for adults exposed to an HbA1c of at least 8% vs. those exposed to an HbA1c between 6% and 7.9%. Those exposed to an HbA1c between 8% and 8.9% for at least 75% of measurements were 2.51 times more likely to develop dementia during follow-up vs. those with less than 10% of measurements in that range (95% CI, 1.23-5.11). Those exposed to an HbA1c of at least 9% for 75% of measurements were 2.13 times more likely to develop dementia during follow-up vs. those with less than 10% of measurements in the same range (95% CI, 1.13-4.01).

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Conversely, adults with prolonged exposure to an HbA1c between 6% and 6.9% were 58% less likely to develop dementia during follow-up vs. those with only 10% of measurements in the same range (adjusted HR = 0.42; 95% CI, 0.21-0.83), whereas those with prolonged exposure to an HbA1c between 7% and 7.9% were 61% less likely to develop dementia vs. those with less than 10% of measurements in the same range (aHR = 0.39; 95% CI, 0.18-0.83).

“Our findings suggest that glycemic levels associated with decreased risk of dementia are largely consistent with currently recommended glycemic targets for older adults with type 1 diabetes,” Lacy said. “Findings also suggest thresholds above which dementia risk increases.”

The researchers noted that they did not have data on cognitive performance measures and were unable to assess glycemic control and changes in cognition or investigate possible reverse effects of cognitive decline on glycemic control.

“A clinical diagnosis of dementia is likely preceded by a period of cognitive decline during which one’s ability to properly manage glycemia may be impacted; this is an especially important limitation in this population of older adults with type 1 diabetes where self-care plays such an important role in disease management,” the researchers wrote. – by Regina Schaffer

For more information:

Mary E. Lacy, PhD, can be reached at the UCSF School of Medicine, Department of Epidemiology and Biostatistics, 550 16th Street, 2nd Floor, Box #0560, San Francisco, CA 94158-2549; email: mary.lacy2@ucsf.edu.

Disclosures: The authors report no relevant financial disclosures.