Impact of the COVID-19 pandemic on body mass index in children and adolescents after kidney transplantation

BACKGROUND: The coronavirus SARS-CoV-2 disease (COVID-19) pandemic affected lifestyles and resulted in significant weight gain in the general population. Its impact on children after kidney transplantation (KTx) is unknown. METHODS: We retrospectively evaluated body mass index (BMI) z-scores during the COVID-19 pandemic in 132 pediatric KTx patients, followed-up at three German hospitals. Among those, serial blood pressure measurements were available for 104 patients. Lipid measurements were available from 74 patients. Patients were categorized according to gender and age group, i.e., children versus adolescents. Data were analyzed by a linear mixed model approach. RESULTS: Before the COVID-19 pandemic, female adolescents presented with higher mean BMI z-scores compared to male adolescents (difference: − 1.05, 95% CI − 1.86 to − 0.24, p = 0.004). No other significant differences could be observed among the other groups. During the COVID-19 pandemic, the mean BMI z-score increased in adolescents (difference: male, 0.23, 95% CI 0.18 to 0.28; female 0.21, 95% CI 0.14 to 0.29, each p < 0.001), but not in children. The BMI z-score was associated with adolescent age, and with the combination of adolescent age, female gender, and the duration of the pandemic (each p < 0.05). During the COVID-19 pandemic, the mean systolic blood pressure z-score significantly increased in female adolescents (difference: 0.47, 95% CI 0.46 to 0.49). CONCLUSIONS: During the COVID-19 pandemic, adolescents in particular showed a significant increase in their BMI z-score after KTx. Additionally, an increase in systolic blood pressure was associated with female adolescents. The findings suggest additional cardiovascular risks in this cohort. GRAPHICAL ABSTRACT: [Figure: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00467-023-05902-4.