Other correlations with NfL are described in a previous publication.18,35 The CSF Aβ42 concentration did not correlate with other factors in Parkinson disease, with the exception that carriers of a higher number of APOE ɛ4 alleles had lower Aβ42, rs = −0.23, P = 0.026. The gene discussed is APOE; the disease is Parkinson disease.