The study “Severity of complications is associated with impaired health-related quality of life in people with type 1 diabetes” provides relevant insights into the relationship between diabetes complications and health-related quality of life (HRQoL) in adults with type 1 diabetes (T1D).

While the absence of a control group and reliance on self-reported outcomes limit the strength of its conclusions, the work is nonetheless supported by a relatively large sample size (n = 1,892) and a multi-center design, which enhance the generalizability of its findings.

The authors assessed HRQoL using both a generic instrument (EQ5D5L) and a diabetes-specific tool (ADDQoL), while the severity of complications was quantified using an adapted Diabetes Complication Severity Index (DCSI).

It is worth noting that the DCSI, originally developed by Young et al. from ICD-9 coding and inspired by Rosenzweig et al., was later modified by Glasheen et al. to accommodate ICD-10 classifications.

Although no general-population comparator was included, the results can be contextualized by referencing a 2018 French national survey in which the average EQ5D-VAS score was 73.4, slightly higher than the mean score of 71.1 reported in the present study.

This difference, though modest, may reflect the impact of living with T1D and its associated complications on perceived health status.

In summary, while the study is well-executed and supported by robust numbers, its contribution lies more in reaffirming known associations than in advancing novel insights.

The results highlight the continued need for complication prevention in T1D, but their clinical impact is primarily confirmatory rather than groundbreaking.

The manuscript is well written, and the study is thoughtfully designed and carefully executed. The abstract clearly summarizes the objectives, methods, and main findings, and the overall presentation is clear and easy to follow.

The study addresses an important and timely topic: the impact of diabetes-related complications on health-related quality of life (HRQoL) in adults with type 1 diabetes.

By leveraging data from a large national cohort (SFDT1), the authors provide robust evidence that higher complication severity, as measured by an adapted Diabetes Complication Score Index (DCSI), is associated with a measurable decline in HRQoL.

The combined use of both a generic instrument (EQ-5D-5L) and a diabetes-specific measure (ADDQoL) strengthens the conclusions and allows for a nuanced assessment across different domains of quality of life.

The findings are clinically relevant, reinforcing the importance of complication prevention and comprehensive care strategies to preserve well-being in adults with type 1 diabetes.

The sample size is large, the methodology is appropriate, and the use of multiple imputation for missing data is a strength.

That said, there are a few points that could be clarified to further improve the manuscript:

The lack of association between complication severity and the anxiety/depression domain of the EQ-5D-5L is intriguing, as mental health is a critical aspect of diabetes care. A more detailed discussion of this result would add value.

While the DCSI provides a convenient global measure of complication severity, it may not fully capture differences in how specific complications (e.g., neuropathy vs. retinopathy) affect quality of life. Some reflection on this limitation would strengthen the interpretation.

The generalizability of the findings should be discussed more explicitly, as this is a French cohort with particular demographic and health system characteristics.

Overall, this is a strong and well-conducted study that makes an important contribution to the literature. I support publication after minor revisions addressing these points.