Lipohypertrophy in Elderly Insulin-Treated Patients With Type 2 Diabetes.

Background: The number of older adults with insulin-treated diabetes mellitus (DM) is steadily increasing worldwide. Errors in the insulin injection technique can lead to skin lipohypertrophy (LH), which is the accumulation of fat cells and fibrin in the subcutaneous tissue. While lipohypertrophic lesions/nodules (LHs) due to incorrect insulin injection techniques are very common, they are often flat and hardly visible and thus require thorough deep palpation examination and ultrasonography (US) for detection. Detection is crucial because such lesions may eventually result in poor diabetes control due to their association with unpredictable insulin release patterns. Skin undergoes fundamental structural changes with aging, possibly increasing the risk for LH. We have therefore investigated the effect of age on the prevalence of LHs and on factors potentially associated with such lesions.

Methods: A total of 1227 insulin-treated outpatients with type 2 DM (T2DM) referred to our diabetes centers were consecutively enrolled in the study. These patients underwent a thorough clinical and US evaluation of the skin at injection sites, as previously described, with up to 95% concordance betweenthe clinical and US screening techniques. Of these 1227 patients, 718 (59%) had LH (LH+) and 509 (41%) were LH-free (LH-). These patients were then assigned to two age class groups (≤ 65 years and > 65 years), and several clinical features, diabetes complication rates, and injection habits were investigated.

Results: Comparison of the two age subgroups revealed that 396 (48%) and 322 (79%) patients in the younger and older groups, respectively, had LHs (p < 0.001). Compared to the younger subgroup, the older subgroup displayed a higher LH rate in the abdomen (52.9 vs. 38.3%; p < 0.01) and a lower rate in the arms (25.4 vs. 35.8%; p < 0.05), thighs (26.7 vs. 33.4%; p < 0.05), and buttocks (4.9 vs. 26.2%; p < 0.01). In older subjects, the most relevant parameters were: habit of injecting insulin into LH nodules (56 vs. 47% [younger subjects]; p < 0.01), rate of post-injection leakage of insulin from injection site (drop-leaking rate; 47 vs. 39% [younger subjects]; p < 0.05), and rate of painful injections (5 vs. 16% [younger subjects]; p < 0.001). Multivariate analysis showed a stronger association between LH and poor habits, as well as between several clinical parameters, among which the most relevant were hypoglycemic events and glycemic variability.

Discussion: The higher rate of post-injection drop-leaking and pain-free injections might find an explanation in skin changes typically observed in older adults, including lower thickness, vascularity and elasticity, and a more prominent fibrous texture, all of which negatively affect tissue distensibility. Consequently, in addition to the well-known association between aging skin impaired drug absorption rate, aging skin displays a progressively decreasing ability to accommodate large volumes of insulin-containing fluid.

Conclusions: The strong association between LH rate and hypoglycemic events plus glycemic variability suggests the need (1) to take specific actions to prevent and control the high risk of acute cardiovascular events expected to occur in older subjects in the case of hypoglycemic events, and (2) to identify suitable strategies to fulfill the difficult task of performing effective educational programs specifically targeted to the elderly.

Trial Registration: Trial registration number 172-11:12.2019, Scientific and Ethical Committee of Campania University "Luigi Vanvitelli", Naples, Italy).