CSF NfL achieved the best diagnostic performance in discriminating IDD from OND patients (age-adjusted AUC = 0.87, 95% confidence interval (CI) 0.80–0.95) with a sensitivity of 0.86 (95% CI 0.74–0.9) and a specificity of 0.83 (95% CI 0.67–0.94), followed by MCI-AD/AD-dem versus OND patients (age-adjusted AUC = 0.84, 95% CI 0.74–0.95) with a sensitivity of 0.94 (95% CI 0.86–1.00) and a specificity of 0.75 (95% CI 0.61–0.89). The gene discussed is NEFL; the disease is intervertebral disk degenerative disorder.