In general linear regression analysis after adjustment for age, sex, hypertension, dyslipidemia, liver function, metabolic syndrome, body mass index, smoking, eGFR, HOMA-IR, and leptin, NAFLD was only negatively associated with Ln SDNN (P<0.05) rather than with Ln rMSSD, Ln HF, and Ln LF. This evidence concerns the gene LEP and metabolic syndrome.