# Epidemiological Trends and Seasonal Patterns in Childhood Type 1 Diabetes: Insights From 2001 to 2024 in Lithuania

## TL;DR

This study shows a significant rise in childhood type 1 diabetes in Lithuania over 24 years, with seasonal patterns and possible links to environmental and viral factors.

## Contribution

The study provides new insights into the rapid increase and seasonal trends of childhood T1D in a genetically homogeneous population.

## Key findings

- The incidence of T1D in Lithuanian children under 15 rose from 10.8 to 36.4 per 100,000 over 24 years.
- New T1D cases peaked during autumn and winter months, possibly linked to reduced sunlight and viral infections.
- The highest increase in T1D incidence was observed in children aged 10–14 years.

## Abstract

Type 1 diabetes (T1D) incidence is rising globally, with significant regional variation. Data from highly homogeneous populations, such as Lithuanian, may contribute to a better understanding of contributing T1D factors. This study examines 24‐year trends in childhood T1D incidence and seasonal patterns in Lithuania.

The annual incidence rates (IRs) were computed utilizing established methodologies per 100,000 children <15 years. The study included 2369 (1181 boys) patients with T1D.

During 2001–2024, the mean IR was 21.4 per 100,000 < 15 years (95% CI: 20.89, 27.28). The incidence rose from 10.8 to 36.4 per 100,000 children under 15 years of age, with notable peaks observed in 2021 and 2022, temporally aligning with the highest COVID‐19 infection waves. Subgroup analysis showed the most rapid increase in young teenagers (10–14 years). Most new cases (63.5%) were diagnosed from September to March.

This study demonstrates a rapidly increasing incidence of T1D in Lithuanian children over a 24‐year period and is one of the highest in European countries. The seasonal distribution of new cases has been speculated to be due to reduced sunlight exposure and lower vitamin D levels, as well as increased school related stress and viral infections during autumn and winter months. However, additional contributing factors are likely involved, underscoring the need for further research.