Evaluation of Renal Function Using Cys-C After Training in a Hot Environment in Collegiate Athlete

In this prospective, comparative study, conducted in hot (August) and non-hot environment (November), we aimed to elucidate the usefulness using Cys-C for assessing renal function after training, focused on a hot environment. Eighteen male collegiate baseball players aged 19.8 ± 1.0 years were included. All participants completed training sessions in both hot and non-hot environments, which involved regular training for 3 h in August and November. The training consisted of 45-min running, 45 min of 20-m dash repetitions, and continuous fungo for 60 min. The wet-bulb globe temperature (WBGT) was recorded over time. Urine samples were collected before and after training, and blood samples were collected after training. The primary outcome measures included the serum creatinine ([Cr]) levels, cystatin-C levels ([Cys-C]), and the estimated glomerular filtration rate based on Cr (Cr eGFR) and Cys-C (Cys-C eGFR). The Risk/Injury/Failure/Loss/End-stage kidney disease classification was used to evaluate acute kidney injury (AKI) based on Cr eGFR and Cys-C eGFR. The median WBGT was 37.9°C in August and 16.0°C in November. The serum [Cr] and [Cys-C] levels were significantly higher in August than those in November (p = 0.003 and p = 0.0004, respectively). Cr eGFR was lower in August than in November (p = 0.005). Although, there was one case in August that met the criteria for AKI based on Cr eGFR, no player in both groups showed decreased renal function based on Cys-C eGFR. Even in a hot environment, Cys-C eGFR is useful for preventing overdiagnosis of AKI for athletes when the baseline is unknown.