Introduction: I am in doubt what problem this manuscript should solve, is it solely a reproducibility study or what are the original or new parts of it?

This should be elaborated further, as referred with 14-16 the answer is known already that there is increased risk of T1D in subjects with the three autoimmune diseases.

Method: Please include the study period for the participants including follow-up period. In the discussion the median follow-up time of 2 years is explained, but this has to elaborated in the method section and also in the results.

Please elaborate more on how the information on relative of T1D was included, which relatives, siblings, parents or?

Please also explain how death of other diseases or lost to follow-up in registries were used in the analysis.

As it is said in method section, no adjustments or multivariate analysis were included in the cox proportional hazard analysis, is this correct?

Also please elaborate, in results section, that the baseline variables are described as imbalanced; this part of your statistical analysis does really need to be explained in methods section, also to ensure transparency.

For the secondary outcome, this will be compared the three diseases inbetween or compared to T1D developers in the control group? Please elaborate also more clear what the index date is defined as?

If you have included information on relatives with T1D, I would recommend you also to analyse how this interferes with the risk of T1D after autoimmun disease or whether their are a higher risk of T1D if you have a relative with T1D compared to one of the three autoimmune diseases.

How is missing information included in analysis, especially on relatives of T1D.

Result: see comments in method section.

Discussion: The age difference in cohorts needs to be questioned also in the view of development of T1D. Missing information needs to be discussed.