The link between diabetes and dementia has been shown to be strong; so strong, in fact, that some doctors think that Alzheimer’s is a form of diabetes. According to Dr. Rachel Whitmer, an epidemiologist at the Kaiser Permanente Northern California Division of Research, people with diabetes have a 75 to 100 percent higher risk of going on to develop Alzheimer’s. Increasingly, scientists are finding evidence that the two diseases are inextricably linked.
But is it diabetes itself that is connected to Alzheimer’s? Or is Alzheimer’s related to the sugar intake that causes Type 2 diabetes? A new longitudinal study that followed 5,189 people over 10 years showed that people with high blood sugar, regardless of whether that made them technically diabetic, had a faster rate of cognitive decline. The higher their blood sugar was, the faster they declined.
Researchers found that elevated levels of the protein HbA1c, which is a measure of overall blood sugar control used in diagnosing diabetes, was linked to poorer cognitive performance and thinking.
The study does more than link cognitive decline to diabetes, said the researchers at Imperial College London and Peking University Clinical Research Institute in Beijing, China. “Our findings show a linear correlation between circulating HbA1c levels and cognitive decline, regardless of diabetic status,” they wrote in the report. “Our findings suggest that interventions that delay diabetes onset, as well as management strategies for blood sugar control, might help alleviate the progression of subsequent cognitive decline over the long-term.”
However, it is still important to note that this was an observational study that draws conclusions from correlations. We know that people with higher blood sugar do worse on memory tests, but we don’t know if that’s why they experience faster cognitive decline.
“One strength of this large study is that it followed people over time to show a faster decline in memory and thinking in those with poorer blood sugar control, but it does not shed any light on the potential mechanisms underlying this decline,” said Dr. David Reynolds, Chief Scientific Officer at Alzheimer’s Research UK.
Just a few months ago, a study found that people whose brains were bad at breaking down glucose, a form of sugar used to fuel the brain, had higher levels of beta-amyloid, the toxic protein associated with Alzheimer’s disease. The study didn’t examine how a diet high in sugar affects glucose breakdown, but study authors hope prescribing lifestyle modifications will come with deeper studies into how sugar intake affects the brain.
This study was published in the journal Diabetologia.