This prospective observational cohort study was registered at ClinicalTrials.gov (NCT04411277). The local institutional review board (IRB) at Universidade Positivo approved the protocol and provided informed consent. Participants were identified by medical records from the Hospital da Cruz Vermelha Brasileira-Filial do Paraná and neuro geriatrician and endocrinology private clinic. Individuals were invited to participate by phone, and interested participants were referred to the Cline Research Center where the study procedures were carried out. Thus, the sample included patients from both public and private health systems.

At the first clinic visit to the research center, after signing an informed consent form, the participants were evaluated for their educational level and presence of comorbidities, including cardiovascular disease, hypertension, and dyslipidemia. Microvascular complications were assessed by a previous eye examination for the presence of retinopathy, foot examination for neuropathy, and the estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI formula.

Screening for the presence of sarcopenia was performed using the SARC-F questionnaire, measuring muscle strength with grip strength using the Saehan dynamometer, and the functional test of getting up from the chair without the support of arms and walking for 3 m, turning 180º, then returning to the sitting position. In addition, body composition analysis using InBody 270 multifrequency bioimpedance was used to calculate appendicular skeletal muscle mass.

Inclusion criteria were age > 65 years, a history of T2DM, BMI between 18·5 and 35 kg/m², HbA1c between 7% and 9%, a stable diabetes medication regimen and body weight over the prior three months, and treatment with insulin and with or without oral agent treatment.

We excluded subjects diagnosed with type 1 diabetes, taking glucagon-like peptide 1 receptor agonists, eGFR < 30 ml/min/1.73 m², anemia (hemoglobin < 11 g), chronic liver disease (ALT > 3x upper limits of normal), use of glucocorticoids within three months prior to the study period, history of neoplasia treatment, and inability by the patient or caretaker to commit to the CGM instructions.

Eligible patients had a CGM sensor (FreeStyle Libre Flash CGM system, Abbott Diabetes Care) inserted for the first time in the posterior upper arm and were recommended to undergo CGM as many times as possible during the day, avoiding scan intervals longer than 8 h. Participants were instructed to return to the research center every 2 weeks, where the CGM data were downloaded and glucose reports were generated for review by the primary provider. CGM monitoring was performed for six consecutive weeks. The first two weeks were considered the baseline, the next two weeks were follow-up 1, and the final two weeks were considered the endpoint.

The research team and healthcare professionals were instructed not to change the treatment regimen except for safety reasons, and in this case, the participants were excluded from data analysis.

The primary outcome was time in range (TIR) between 70 and 180 mg/dL, and secondary outcomes were time below range (TBR) (< 70 mg/dL and < 54 mg/dL), time above range (TAR) (> 180 mg/dL, and > 250 mg/dL), glucose variability (GV) (calculated by % coefficient of variation, %CV = standard deviation (SD)/mean glucose x 100%), and adherence to CGM use (the percentage of captured sensor data). TIR, TBR, and TAR were expressed as percentages of the time per day. We also evaluated the prevalence of TIR ≥ 70% of the day, TBR (< 70 mg/dL) > 4% of the day, TBR (< 54 mg/dL) > 1% of the day, TAR (> 180 mg/dL) > 25% of the day, TAR (> 250 mg/dL) > 5% of the day, and the GV > 36% for each timepoint of the study (baseline, follow-up 1, and endpoint).

We used measures of central tendency (mean and median), variability (SD, interquartile range (IQR)), absolute (n), and relative (%) frequencies to describe participant characteristics and glucose profiles. A set of eight linear regressions with random intercept (participants) and slopes (time points) verified the changes in TBR (Overall: <70 mg/dL; TBR 1 (54–70 mg/dL, and TBR 2 (< 54 mg/dL)), TIR, TAR (> 180–250 mg/dL and > 250 mg/dL), GV, and glucose management indicator (GMI) across the three time points (baseline, follow-up 1 and endpoint) controlled by gender, age, educational level, and health system (private or public). We further explored the covariance between the intercept and slope to identify the influence of baseline values on the changes over time. The results were expressed in regression coefficients (β) and 95% confidence intervals (95% CI). The statistical significance was set at p < 0.05. The sample size showed a power of 0.80 to identify regression coefficients equal to or higher than ± 0.43 with an alpha of 95%. All statistical analyses were performed using Stata MP 14.1.