People with diabetes suffer from more blindness, more small nerve damage (especially in the feet) and more kidney damage, as well as heart disease, strokes and problems with blood supply to the feet and legs. A meta‐analysis of 28 prospective observational studies found that people with type 2 diabetes are 73 per cent more likely to get dementia, 56 per cent more likely to get Alzheimer’s disease and 127 per cent more likely to be diagnosed with vascular dementia.
What’s messy is that all the factors that make diabetes more likely to develop in someone are also risk factors for dementia. We know that insulin resistance underpins diabetes. And brain scans of patients with dementia often show patchy areas in the brain where there is reduced glucose metabolism. Many researchers have postulated that insulin resistance within the brain might drive the development of Alzheimer’s disease, with many calling it brain-specific ‘type 3 diabetes’.
Is it the diabetes that causes the dementia or are they both diseases of poor lifestyle and so often crop up together? That’s particularly important when looking at trials of anti-diabetic medications for the prevention of dementia or to stop it from getting worse.
And those trials are a bit of a mixed bag, to be honest. The authors of a 2017 Cochrane review of seven randomised controlled trials concluded: ‘We found no good evidence that any specific treatment or treatment strategy for type 2 diabetes can prevent or delay cognitive impairment.’ In fact, a couple of trials for some diabetic medicines found they could make cognitive impairment worse.
I wanted to say a quick word about metformin, which is the most popular ‘first line’ medication to treat diabetes. I was intrigued to read the findings from a Canadian study published in 2020. The study followed 2000 people with diabetes taking various medications over time. Here’s what they found: among the diabetics who had normal cognitive test results at the start of the study, those taking metformin did better on memory tests when measured after two weeks and again after two years than people taking other diabetic drugs – all of which didn’t affect memory performance either way. (With the exception of a group of drugs called Sulfonylureas that can cause low blood sugar as a side effect. The memories of the participants taking this got worse over time.)
As part of the same study, the authors looked at people specifically carrying the APOE gene. Those who took a diabetes drug class called DPP4 inhibitors had a much slower cognitive decline than non-carriers. But strangely, metformin didn’t give any cognitive benefits to this group with the APOE gene.
The bottom line is: if you have diabetes, you’re going to need a treatment. Maybe you would choose metformin, especially if you don’t carry the APOE gene. If you do have that gene, you might opt for a DPP4 inhibitor. But mostly you want to have a great diet, one that includes lots of healthy veggies, fruit, wholegrains and lean protein foods, and as little junk food and soft drink as possible. Plus, you really ought to increase your exercise, sleep well and control your blood pressure and cholesterol.