Scientists find stronger link between sugar and Alzheimer’s disease

Scientists at the English Longitudinal Study of Aging (ELSA) have found increasing evidence that high sugar intake is linked to Alzheimer’s disease, in an ongoing assessment dating back to 2002.

The comprehensive study observed over five thousand people over 50, with an average age of 66, 55% of whom were women.  It assessed the participants’ cognitive function over ten years, closely monitoring their glycated haemoglobin (HbA1c) levels, a measure of blood sugar over time. Previous studies have shown a link between diabetes and cognitive disorders, but measuring HbA1c is a unique approach.

“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,” said Imperial College London epidemiologist Wuxiang Xie, who led the research.

According to the research, all participants showed some level of cognitive decline over the ten year time frame due to natural ageing but those with higher levels of glycated haemoglobin experienced a faster rate of cognitive decline. ELSA conducted tests to measure the individuals’ cognitive, memory, and executive functions – a set of neurological skills pertaining to mental control and self-regulation.

Diabetes and Alzheimer’s

New York University professor Melissa Schilling found a connection between diabetes and Alzheimer’s disease in 2016. She found that people who suffer from type-2 diabetes are around twice as likely to suffer from Alzheimer’s in later life, with this risk being even higher for people who are treated with insulin, suggesting the hormone has an impact on cognitive disorder. Numerous studies have confirmed that hyperinsulinemia increases the risk of Alzheimer’s.  Oddly, those with type-1 diabetes, who produce no insulin at all, are also at a higher risk of contracting Alzheimer’s.

The answer to this peculiarity, according to Schilling, is that the insulin-degrading enzyme which breaks down insulin and amyloid proteins in the brain are the same proteins that build up to cause Alzheimer’s disease. People who don’t have enough insulin are unable to break down protein brain clumps, while those who artificially inject insulin end up with a surplus, which focuses on breaking down the insulin proteins meaning there is not enough to break down the amyloid proteins.

ELSAs findings

ELSA has discovered a link beyond diabetes and Alzheimer’s, suggesting that HbA1c levels were measured regardless of whether the participant was diabetic.

HbA1c levels in healthy subjects are lower than 42 millimoles per mole (mmol/mol), or below 6%, whereas diabetics were exhibiting levels of 48mmol/mol, around 6.5% or higher. Those diagnosed as ‘pre-diabetic’ would fall in the middle, or 42-47mmol/mol.

On this basis, the researchers found a more tentative link between higher HbA1c levels and Alzheimer’s, saying “Our findings show a linear correlation between circulating HbA1c levels and cognitive decline, regardless of diabetic status.”

ELSA conceded that while it was too early to understand the dietary implications for those suffering from high blood sugar, the research has strengthened evidence that consumers should be more careful about their diets in order to prevent the development of type-2 diabetes and a higher risk of Alzheimer’s.

“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 Alzheimer’s Research UK’s chief scientific officer David Reynolds.

In 2012, Mayo Clinic epidemiologist Rosebud Roberts conducted an experiment that split 1,000 participants into four groups based on their carbohydrates intake. The group that ate the most carbs had an 80% higher chance of developing mild cognitive impairment than those in the lowest carb group.

Roberts warned: “Just because you don’t have type-2 diabetes doesn’t mean you can eat whatever carbs you want…especially if you’re not active. [What we eat is] a big factor in maintaining control of our destiny.”