Our findings provide additional prospective associations that, compared to the reference group (USG < 1.010, corresponding to other markers of good hydration, e.g., plasma copeptin < 3pmol/L, plasma osmolality 285 mOsmol/kg, and blood sodium ions 140 mmol/L) [13], under-hydration (1.020 ≤ USG < 1.030 or 1.020 ≤ USG < 1.025) and clinical dehydration (USG ≥ 1.030 or USG ≥ 1.025) both increased the risk of T2D. The gene discussed is AVP; the disease is type 2 diabetes mellitus.