A great deal of research in recent years has explored the link between blood glucose and cognitive decline — in type 1 and in type 2 diabetes, as well as in prediabetes — and several studies have found that elevated glucose levels, over time, raise the risk for cognitive problems. But most of these studies have looked at long-term blood glucose control, as measured by A1C — and, as a result, they haven’t taken into account the effects of blood glucose variation on cognitive decline. There is reason to believe, based on previous research, that both high and low blood glucose levels may raise the risk for cognitive problems.
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For the latest study, researchers examined the impact of both very high and very low blood glucose on the risk for dementia in 2,821 older adults with type 1, with an average age of 56. Participants were followed for a total of about 18 years, between 1997 and 2015. During this time period and slightly before it (starting in 1996), episodes of high or low blood glucose that required emergency attention or hospitalization were recorded. Any diagnosis of dementia was also recorded during this period, through September of 2015. To isolate the effects of very high or very low blood glucose on dementia risk, the researchers adjusted for participants’ age, sex, race or ethnicity, A1C levels, and diagnoses of depression, stroke, or nephropathy (diabetic kidney disease).
Episodes of very low, high blood glucose linked to dementia risk
During an average follow-up period of 6.9 years per participant, 153 (5.4%) developed dementia. At the same time, 398 participants (14%) experienced at least one episode of severely low blood glucose, 335 (12%) experienced severely high blood glucose, and 87 (3%) experienced both. After adjusting for other factors as described above, the researchers found that participants who experienced very low blood glucose were 66% more likely to develop dementia than those who didn’t have such an event. Participants who experienced very high blood glucose, on the other hand, were more than twice as likely — 111% more likely — to develop dementia compared with those who didn’t have such an event. And in those who experienced both very high and very low blood glucose, the risk for dementia was over six times as high — 520% higher — compared with those who didn’t have both types of events.
“Our findings suggest that exposure to severe glycemic events may have long-term consequences on brain health and should be considered additional motivation for people with diabetes to avoid severe glycemic events throughout their lifetime,” said study author Rachel A. Whitmer, PhD, professor and chief of the Division of Epidemiology in the Department of Public Health Sciences at the UC Davis School of Medicine, in a press release.
Want to learn more about maintaining cognitive health with diabetes? Read “Nine Tips to Keep Your Memory With Diabetes,” “Keeping Your Brain Strong With Diabetes” and “Memory Fitness: How to Get It, How to Keep It.”