Upper extremity impairments in type 1 diabetes in comparison to matched controls without diabetes : associations to the IGF-system, metabolic factors, disability and quality of life

Abstract: Compared with the general population, people with type 1 diabetes (T1D) more often exhibit pathological alterations in musculoskeletal tissue (impairments). Some of these impairments involve the upper extremities, i.e., the shoulders, hands, and fingers. Although present in diabetes, these complications are underdiagnosed and not actively searched for during routine clinical examinations. Furthermore, much is still unclear about these impairments, specifically regarding their etiology, risk factors, and consequences on daily life activities and quality of life. The growth hormone (GH)/insulinlike growth factor (IGF)-system is known to be affected in diabetes, but whether this is involved in upper extremity impairments (UEIs) is unclear. The aim of this thesis was to describe the prevalence of UEIs in patients with diabetes compared with controls. Furthermore, we aimed to search for risk factors of UEIs, and elucidate the impact of UEIs on daily life activities and health-related quality of life (HRQOL). We used two cohorts; the LedIG cohort (papers I–III), a large population-based study in which all patients with a long duration of T1D (>20 years), aged <67 years, living in the south-east region of Sweden were invited to participate, as well as matched controls without diabetes. This study was based on questionnaires as well as blood samples from the participants. The last paper (IV) included a smaller cohort (n=69) of patients with T1D, who both completed a questionnaire and were the subjects of a clinical examination.Paper I: The UEIs were common in diabetes, with a prevalence of up to 48%. Hand paresthesia was the most common impairment, followed by shoulder pain and stiffness. The prevalence of UEIs was 2–4 times higher in patients than in controls and was associated with more activity limitations. Risk factors were heterogeneous for the different UEIs and included female sex, increasing age, longer duration of diabetes, and poor glycemic control.Paper II: The GH-IGF-axis is important for the growth and function of musculoskeletal tissues. We examined differences in the IGF system between patients with T1D on subcutaneous insulin treatment and controls. We found lower levels of IGF-I and insulinlike growth factor-binding protein (IGFBP)-3 and higher levels of GH and IGFBP-1 in patients with T1D than in controls. The largest difference was found in IGFBP-1, and this probably reflected insulin deficiency. The IGF-I levels were increased with increasing insulin doses. However, even at very high insulin doses (>1 U/kg) the IGF-I Z-score was subnormal, indicating that IGF-I cannot be normalized by subcutaneous insulin treatment. Residual endogenous insulin secretion counteracted these alterations. Furthermore, we investigated possible relationships between UEIs and IGF-I, and found no association.Paper III: The HRQOL was lower in patients with T1D than in controls. Patients with shoulder impairments, hand paresthesia, and hand stiffness, but not finger impairments, had lower HRQOL scores than patients without these impairments. The patients with T1D showed a higher frequency of sick leave than controls, and a common reason for this was musculoskeletal impairments.Paper IV: In addition to the self-reported UEIs, the prevalence of UEIs was also investigated by clinical examination. Clinical UEIs were found in 65% of the participants, with shoulder test (hands against back), prayer sign test, and the Phalen’s and Tinel’s tests being most prevalent. We compared self-reported UEIs to clinical UEIs and found that self-reported impairments were associated with clinical examination. We also found that self-reported shoulder impairments, reduced hand strength, and previous surgery for carpal tunnel syndrome and trigger finger were associated with several other UEIs.In current diabetic care, there is no established routine to capture UEIs, as opposed to other known diabetes complications. We show that UEIs are more common in patients with T1D than in controls, and that they are related to impaired HRQOL and daily life activity limitations. Clinical routines including self-reported UEIs, e.g. shoulder stiffness and reduced hand strength, might be used to identify patients with UEIs in need of clinical investigation, enhanced preventive and therapeutic strategies, as well as rehabilitative interventions.