Diabetes mellitus as a risk factor for compression neuropathy: a longitudinal cohort study from southern Sweden

INTRODUCTION: Compression neuropathies (CN) in the upper extremity, the most common being carpal tunnel syndrome (CTS) and ulnar nerve entrapment (UNE), are frequent among patients with diabetes mellitus (DM). Earlier studies have shown contradicting results regarding DM as a risk factor for CN. Thus, the aim of the present population-based, longitudinal study was to explore potential associations between DM, CTS, and UNE during long-term follow-up. RESEARCH DESIGN AND METHODS: A total of 30 466 participants aged 46–73 years, included in the population-based Malmö Diet and Cancer Study during 1991–1996, were followed up in Swedish national registries regarding incident CTS and UNE until 2016. Associations between prevalent DM at baseline and incident CTS or UNE were calculated using Cox proportional hazard models, adjusted for baseline confounders, such as sex, age at study entry, smoking, hypertension, use of antihypertensive treatment, alcohol consumption, and body mass index (BMI). HbA1c and fasting plasma glucose levels had been measured at baseline in a subgroup of 5508 participants and were related to incident CTS and UNE in age and sex-adjusted binary logistic regression models. RESULTS: A total of 1081 participants developed CTS and 223 participants developed UNE during a median follow-up of 21 years. Participants with incident CTS or UNE had higher prevalence of DM and higher BMI at baseline. Using multivariate Cox regression models, prevalent DM at baseline was independently associated with both incident CTS (HR 2.10; 95% CI 1.65 to 2.70, p<0.0001) and incident UNE (HR 2.20; 95% CI 1.30 to 3.74, p=0.003). Higher levels of HbA1c and plasma glucose were associated with an increased risk for CTS, but not for UNE. CONCLUSION: This study establishes DM as a major risk factor in the development of both CTS and UNE. Furthermore, a higher BMI is associated with both CTS and UNE. Finally, hyperglycemia seems to affect the median and ulnar nerves differently.