Faster progression to severe diabetes observed in people with learning disabilities

People with learning disabilities progress faster to severe type 2 diabetes and are at greater risk of dying from their condition than people without these disabilities, suggests research published in the open access journal BMJ Open Diabetes Research & Control.

This is despite having better overall blood glucose control and similar risks of vascular complications, the findings indicate.

Around 1.5 million people (950,000 adults) in the UK have a learning disability, which includes conditions such as Down syndrome and cerebral palsy, note the researchers. 

Type 2 diabetes in those with learning disabilities can be challenging as it requires a substantial amount of monitoring and management, which they may not always be able to do, potentially compromising their blood glucose control, explain the researchers.

But there's been no large study on the potential impact of learning disabilities on the outcomes of type 2 diabetes, including blood glucose control, progression to microvascular and macrovascular complications, initiation of insulin therapy (proxy for severe disease), and risk of death, they add.

Macrovascular complications refer to stroke, coronary heart disease, heart failure, peripheral vascular disease, or amputation more than 6 months after diagnosis of type 2 diabetes. Microvascular complications refer to diabetic nephropathy, retinopathy, or neuropathy.

In a bid to plug this knowledge gap, the researchers extracted anonymized medical records for 352,215 adults newly diagnosed with type 2 diabetes in primary care between January 2004 and January 2021 from the UK Clinical Practice Research Datalink (CPRD) GOLD.

Of these, 280,300 met the eligibility criteria for inclusion in the study, 2074 of whom had a learning disability when they were diagnosed.

They tended to be younger (average age 51 vs 64) and have a shorter monitoring period. And they included higher proportions of men, people of White ethnicity, people living with severe obesity and in areas of greatest deprivation than those without learning disabilities.

They were also more likely to be taking medication for diabetes and high blood pressure and to have more complications related to diabetes at the time of their diagnosis. 

Even after adjusting for these potentially influential risk factors they were 19% less likely to have poor blood glucose control than those without learning disabilities 5 years after diagnosis.

But they were 20% more likely to progress faster to severe disease and the need for insulin therapy than those who didn't have learning disabilities. 

And they were around twice as likely to die from any cause and specifically from diabetes despite having similar risks of vascular complications as those who didn't have learning disabilities.

This is an observational study, and as such, can't establish cause and effect, and the researchers acknowledge that large numbers of values for the outcome variables for blood glucose control were missing among those with learning disabilities. Complication rates may therefore have either been underdiagnosed or under-recorded, they suggest. 

"Our finding of higher rates of insulin initiation in those with learning disabilities warrants further investigation into whether this is due to poorer glycemic control at presentation (and therefore faster advancing type 2 diabetes) or due to having a greater degree of clinical surveillance," say the researchers.

"Future research into the mechanisms behind this could help reduce health disparities for people with [type 2 diabetes] and learning disabilities," they add.