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.