The studies included in the meta-analysis used different indicators to diagnose type 2 diabetes, including fasting plasma glucose (FPG) ≥ 7 mmol/L, HbA1c ≥ 6.5%, random sample plasma glucose concentration ≥ 11.1 mmol/L, WHO criteria, physicians’ diagnosis reports, and receiving insulin or other oral hypoglycemic drugs based on central pharmacy records. The gene discussed is INS; the disease is type 2 diabetes mellitus.