Background: Diabetes Mellitus (DM) is a chronic disease that affects millions of people worldwide. More than 95% of cases are type 2 diabetes mellitus (T2DM). In recent years, diabetes management has evolved with the introduction of continuous glucose monitoring (CGM) devices. These devices implanted under the skin allow continuous measurement of glucose levels monitoring glucose trends and the rate at which glucose level rise and fall without the need for capillary glycaemias test. While studies demostrate the effectiveness of CGM devices in controlling glucose levels in adults with T2DM, there is no evidence related to quality of life in this patients.

Hypothesis: The use of CGM in people with T2DM improves their quality of life, reduces distress about the disease, reduces fear of hypoglycaemia, increases detection of hypoglycaemia, and improves metabolic control.

Objectives: To assess quality of life, diabetes distress, fear of hypoglycaemia, detection of hypoglycaemia, and metabolic control in people with T2DM before and after the use of CGM sensors.

Methodology: Prospective observational pre-post unblinded study. Adults with type 2 diabetes using a CGM device in the primary care setting will be followed for 12 months. They will be asked to complete 5 questionnaires at baseline, and 4 questionnaires at 3, 6 and 12 months. No other activity that differs from usual clinical practice will be performed.

Data analysis: a descriptive analysis of the main study variables will be carried out and the differences in the data before and after the intervention will be analysed using the chi-square test for qualitative variables, and the Student's t-test for quantitative variables. Statistical significance will be accepted at a p-value < 0.05.

Applicability and relevance: The results of the study will provide information on whether CGM devices improve quality of life and glycaemic control in people with type 2 diabetes. With these results it will be possible to assess whether it is beneficial to extend funding for CGM devices to more of the population than is currently the case.

Study development: The recruitment period runs from September 2024 to February 2025. Participants will be recruited by health professionals (nurse or doctor) CGM referents from each of the 20 primary care centres in the Camp de Tarragona health region. Sampling will be by convenience, all persons who meet the inclusion criteria and none of the exclusion criteria will be offered to participate in the study. Participants must sign an informed consent and their data will be coded.

Participants will be asked to fill in 5 questionnaires at the beginning of the study:

• Sociodemographic questionnaire created ad hoc to know the profile of the patients.
• EsDQOL questionnaire that assesses the quality of life related to diabetes.
• DDS17 questionnaire that assesses diabetes-related distress.
• EsHFS questionnaire that assesses fear of hypoglycaemia.
• Clarke Test that assesses the detection of hypoglycaemia.

The EsDQOL, DDS17, EsHFS and Clarke Test questionnaires must be repeated at 3, 6 and 12 months after the start of the study. Participants will be called to their primary care centre of reference to fill in the questionnaires themselves and these will be kept on paper at the centre until data analysis.

To assess metabolic control, the data provided by the CGM sensor will be used and the results of the AGP (Ambulatory Glucose Profile) report of the first 2 weeks will be compared with the data at 3, 6 and 12 months. No analytical tests or capillary blood glucose measurements will be requested.

Data analysis: A descriptive analysis of the main study variables will be performed using percentages for qualitative variables and mean and standard deviation for quantitative variables. To analyse the differences in the data before and after the intervention, chi-square tests will be used for qualitative variables and the Student's t-test for quantitative variables. Statistical significance will be accepted with a p-value <0.05. Data will be analysed using SPSS statistical software version 23 or later.

Sample calculation: Accepting an alpha risk of 0.05 and a statistical power greater than 0.8 in a bilateral contrast, 55 subjects are required to detect as statistically significant a difference equal to or greater than 9 units in the EsDQOL questionnaire (main study variable). A common standard deviation of 23.65 is estimated. A loss to follow-up rate of 0% is estimated. [GRANMO sample size calculator v7.10 available at Calculator (laalamedilla.org)].

Inclusion Criteria:

• Treatment with intensive insulin therapy (basal bolus regimen with 3 or more daily doses of insulin).
• Perform 6 or more daily capillary glycaemia determinations.
• Be willing to use a CGM device for at least 70% of the time.
• Undergo training on the use of the CGM device by the centre's CGM referent.
• Agree to participate in the study.

Exclusion Criteria:

• Cognitive impairment measured by Pfeiffer test with a score of 3 or more errors.
• Previous use of a CGM device.
• Pregnancy.
• Being institutionalised.
• Having participated in another research study related to diabetes mellitus within the last year.
• Not having proper handling of the CGM device: inability to download glycaemic control data, inability to keep the sensor attached to the skin, not understanding how it works, etc.

The study population is adults in an industrialised country with a diagnosis of type 2 diabetes with intensive insulin regimen who will start using a CGM sensor. Participants will be recruited from primary care centres in the Camp de Tarragona health region following inclusion and exclusion criteria. Depending on the location of the primary care centre, the population may be from an urban, semi-urban, or rural setting.