Risk of type 2 diabetes and risk of dementia both increase with age, so it is perhaps not surprising that some elderly patients exhibit both conditions simultaneously.1 However, is there more to this connection than aging? Could there be a deeper link between the two?
Research supporting a direct link
Multiple studies have shown that recurring episodes of hypoglycemia are associated with dementia and cognitive impairment.1–3 For example, a study evaluating data from the Korean National Health Insurance Service Senior cohort, which covers more than 10% of the elderly population in South Korea, found that individuals who had experienced hypoglycemic episodes showed a greater risk of dementia than those without a history of hypoglycemia.4
However, according to other studies, this relationship appears to be a two-way street. These studies suggest that hypoglycemia may increase the risk of dementia, and individuals with dementia or cognitive impairment may have a higher risk of hypoglycemic episodes.2,3 For example, a Japanese study found that the risk of hypoglycemia increased with progression of cognitive impairment in individuals aged 65 years or older.5
At the same time, an association between hypoglycemia and dementia does not necessarily mean that one caused the other. “There is a huge difference between ‘association’ and ‘cause,’” says Dr. Insa Feinkohl, a researcher at the Molecular Epidemiology Research Group, Max-Delbrueck-Center for Molecular Medicine in the Helmholtz Association, Germany. “Finding an association of hypoglycemia with future cognitive impairment in an epidemiological research study does not mean that hypoglycemia caused impairment.”
Alternative explanations for this association
It is possible that the association between hypoglycemia and dementia might not be a direct cause-and-effect relationship. Indeed, cognitive impairment may reduce an individual’s ability to manage their condition, maintain adequate nutrition, or use glucose-lowering medications appropriately. Such a situation could result in hypoglycemia.
Another possibility is that factors that increase risk of developing hypoglycemia might also predispose an individual to cognitive impairment and dementia. There is also speculation that hypoglycemia could be a marker of cognitive decline instead of being a cause or risk for such decline.2
Research against a direct link
Several studies have shown no association between hypoglycemia and dementia in older people with type 2 diabetes:
• In the Outcome Reduction with Initial Glargine Intervention (ORIGIN), hypoglycemia did not increase the risk of cognitive impairment in 11,495 individuals who had dysglycemia (abnormal levels of sugar in the blood) but no cognitive impairment at the beginning of the study.2
• In the ADVANCE (Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation) study and the ACCORD MIND (Action to Control Cardiovascular Risk in Diabetes Memory in Diabetes) study, type 2 patients receiving intensive glycemic control treatment showed more episodes of hypoglycemia but a similar rate of cognitive impairment compared with the group that was given standard glycemic control therapy.3 This study indicates no association between hypoglycemia and cognitive decline.
A grey area
So, what is the conclusion and does type 2 diabetes increase risk of dementia in older people, and vice versa?
According to Dr. Feinkohl, “The relationship of hypoglycemia and cognitive impairment is complex and not well understood. While cognitive impairment in older age appears to put people with diabetes at risk of experiencing hypoglycemia in the future (for instance, because they become less able to manage their diabetes), we do not currently know whether a prior history of hypoglycemia increases the risk of cognitive impairment. Some studies point towards this, but others do not.”
The key takeaway
The American Diabetes Association recommends screening for cognitive impairment in individuals with diabetes who are 65 years or older.6 While the key takeaway from this review of the evidence is not to dwell on a potential link between hypoglycemia and dementia in type 2 diabetes, screening is a sensible step to take as a precautionary measure. Not only can it help put your mind at ease, but it can also ensure that any issues are identified and addressed early. For example, managing or preventing risk factors for cardiovascular disease may improve cognitive symptoms if initiated early. This strategy may include treatment for existing cardiovascular conditions and making appropriate lifestyle changes such as improving nutrition and getting adequate exercise. Additionally, it has been proposed that the presence of cognitive impairment may indicate a need for less intensive glycemic control, so early identification allows diabetes practitioners to change the treatment regimen if necessary.
Want to learn more about hypoglycemia? Read “Understanding Hypoglycemia,” “Exorcising the Specter of Overnight Hypoglycemia” and “Hypoglycemia Unawareness.” And to learn more about improving memory, read “Memory Fitness” and “Nine Tips to Improve Your Memory With Diabetes.”