Environmental Determinants of Type 1 Diabetes Risk

Inclusion Criteria:

1. Individuals with type 1 diabetes (no age restriction):

   * Clinically diagnosed with T1D by a specialist.
   * Meeting any one of the following conditions:(1) Age of onset \< 15 years;(2) No overweight or obesity at onset;(3) History of ketoacidosis.
   * Insulin-dependent since disease onset;
   * Positive for at least one islet autoantibody (GADA, IA-2A, ZnT8A, IAA, ICA);
   * Disease duration ≤ 3 years.
2. First-degree relatives:

   * Parents, siblings, or children of an individual with T1D.
   * Age ≤ 45 years.

Exclusion Criteria:

1. Individuals with type 1 diabetes

   * Gestational diabetes.
   * Confirmed monogenic diabetes.
   * Secondary diabetes.
   * Type 2 diabetes.
   * Other specific types of diabetes.
2. First-degree relatives:

   * Diagnosed with diabetes before screening;
   * Previous or current use of glucose-lowering drugs.

Common exclusion criteria:

* Severe active disease or a condition likely to substantially affect life expectancy, including malignancy or severe cardiac, pulmonary, hepatic, or renal disease.
* A condition that may require immunosuppressive therapy during the study period.
* Current systemic immunosuppressive therapy.
* Current systemic glucocorticoid therapy.
* Participation in another drug or medical device trial during recruitment or the study period.
* History of major surgery or severe trauma.