Comparison of BMI and HbA1c changes before and during the COVID-19 pandemic in type 1 diabetes: a longitudinal population-based study.

Purpose: To compare the changes in body weight and glycemic control before and during the COVID-19 pandemic in people with type 1 diabetes (T1D). Methods: In 47,065 individuals with T1D from the German Diabetes Prospective Follow-up Registry (DPV), we compared the adjusted mean changes in BMI-Z-scores and HbA1c as well as the distribution of individual changes between four periods from March 2018 to February 2022, by sex and age group (4- < 11, 11- < 16, 16-50 years). Results: At population level, the only significant pandemic effects were a slight increase in BMI Z-score in prepubertal children (girls: + 0.03 in the first COVID year vs. before, P < 0.01; boys: + 0.04, P < 0.01) as well as a stabilization of HbA1c in all subgroups or even improvement in women (- 0.08%, P < 0.01). At individual level, however, heterogeneity increased significantly (p < 0.01), especially in children. More prepubertal children gained weight (girls: 45% vs. 35% before COVID; boys: 39% vs. 33%). More pubertal girls lost weight (30% vs. 21%) and fewer gained weight (43% vs. 54%). More children had a decreasing HbA1c (prepubertal group: 29% vs. 22%; pubertal girls: 33% vs. 28%; pubertal boys: 32% vs. 25%) and fewer had increasing values. More women had stable HbA1c and fewer had increasing values (30% vs. 37%). In men, no significant changes were observed. Conclusion: This real-world analysis shows no detrimental consequences of the two first COVID years on weight and HbA1c in T1D on average, but reveals, beyond the mean trends, a greater variability at the individual level.