Untreated high blood sugar can cause painful problems such as frozen shoulder, agonising wrist condition carpal tunnel syndrome, and Dupuytren’s disease – also known as ‘claw hand’ – new research has shown.

High blood sugar, which affects those with diabetes, has long been linked to problems in the legs and feet, sometimes causing painful ulcers that can become infected and even lead to amputations.

The condition has also been connected to muscle and bone problems in the upper body, but a study by scientists at the University of Exeter is the first to provide evidence that these are directly caused by high blood sugar.

The researchers analysed genetic data from 370,000 participants in the UK Biobank study – a large-scale biomedical database containing anonymised genetic, lifestyle and health information.

They found strong evidence that those with a higher chance of developing uncontrolled high blood sugar, known as hyperglycaemia, were also more likely to develop four upper limb problems.

Untreated high blood sugar can cause painful problems such as frozen shoulder, research suggests

These are frozen shoulder, where the connective tissue in the joint thickens leading to stiffness and discomfort; carpal tunnel syndrome, where trapped nerves in the wrist cause numbness, tingling and pins and needles; Dupuytren’s contracture, where connective tissue in the hand thickens and tightens, causing the fingers to bend inward; and trigger finger, a similar condition that affects just one finger.

The study suggests that, over time, hyperglycaemia increases the levels of a substance in the body called advanced glycation end products (AGEs), which form when proteins, fats and DNA mix with sugars in the bloodstream.

It’s believed that a build-up of AGEs – found in the hands of people with Dupuytren’s disease and in the shoulders of those with frozen shoulder – are what causes the damage and thickening of the tendons, joints and connective tissues which cause the problems.

The leader of the research, Dr Harry Green of the University of Exeter Medical School, says: ‘Our study consistently demonstrates that having high blood sugar over the long term causes these upper limb conditions.

‘We can now classify them as diabetes complications. Clinicians treating diabetes patients should be aware of these complications in clinic, so they can advise on the best treatment pathways.’

High blood sugar, which affects those with diabetes , has long been linked to problems in the legs and feet, sometimes causing painful ulcers that can become infected and even lead to amputations