Carpal Tunnel Syndrome May Be Harbinger of Type 2 Diabetes

The association between neuropathies and diabetes is well established. Up to 20% of diabetic patients have a compression neuropathy such as carpal tunnel syndrome (CTS), and in patients with limited joint mobility, the incidence can be as high as 75%. A new report suggests CTS can precede the diagnosis of diabetes by up to 10 years.¹

The authors analyzed data from a large registry in the U.K. and identified patients diagnosed with diabetes during 2003–2004. They then reviewed the medical records of these 2,655 patients, searching for the initial date and diagnosis of CTS, Bell's palsy, and other peripheral nerve disorders. Patients with other known risk factors for CTS, such as thyroid disease, rheumatoid arthritis, osteoarthritis, or prior wrist trauma, were excluded. The investigators found that the incidence of CTS in patients with pre-diabetes was increased, with a relative risk of 1.63. There was an increased incidence of Bell's palsy, but not other peripheral nerve disorders, in these patients.

“Hyperglycemia and associated metabolic abnormalities may contribute to causing these important focal peripheral nerve disorders before the diagnosis of diabetes,” the authors conclude. Lead author Martin Gulliford, MD, of King's College London, says it would make sense to assess blood glucose control in patients diagnosed with CTS.

The study is a follow-up to a report published last year by the same authors looking at health care utilization in patients prior to a diagnosis of diabetes. Compared with a control group, physician visits and medication prescriptions increased 5 years preceding diagnosis.²

These and other studies remind clinicians that morbidity from diabetes can begin years before a formal diagnosis is made. A 2003 study in Neurology found that 56% of patients with idiopathic peripheral neuropathy had abnormal oral glucose tolerance tests.³ The National Diabetes Group determined that retinopathy begins about 4–7 years before a diagnosis of diabetes.⁴ This research underscores the importance of early detection and treatment of patients with impaired glucose tolerance.

The implication for physicians of the CTS study's findings is intriguing. It is the first to review a diabetic cohort retrospectively for peripheral nerve disorders. Knowing which conditions commonly foreshadow diabetes helps physicians identify and screen those patients at increased risk. An oral glucose tolerance test should be considered for patients with a high pre-test probability of having diabetes yet who have a normal fasting glucose. ▪