*2.1. Participants*

This case-control survey was conducted among 219 young Polish women. The study group consisted of 113 persons with T1DM (52% used MDIs and 48% used CSII) and the control group contained 106 healthy individuals. The median ages in T1DM and healthy groups were 22 and 25 years, respectively. The online survey was carried out in December 2020, during the peak of the second wave of the COVID-19 pandemic, through private groups on social media platforms. The main criterion for inclusion in the study group was young age (between 16 and 35 years) and residence in Warmian-Masurian or Podlaskie Voivodeships. Responses from participants residing abroad, a different type of DM than the type 1 and people who had ever tested positive for the new coronavirus have been rejected. At the same time, a survey was conducted among healthy volunteers who expressed their willingness to participate in our study. Each person was informed that the completed questionnaire was anonymous and confidential. The questionnaire could be completed only once and it was possible to withdraw from the survey at any given moment, then the answers were not saved. By completing and sending the questionnaire, respondents confirmed consent to participate in the study. No personal data were required. The study had obtained the consent of the Bioethical Commission of the Medical University of Bialystok No. R-I-002/587/2019.
