Predictive value of serum neurofilament light chain for persistent cognitive deficits in elderly depressive patients

Elderly patients with depression often exhibit severe cognitive impairment. Neuropsychological tests and psychiatric exploration may not differentiate between reversible cognitive deficits due to depression and persistent cognitive impairment due to dementia. Neurofilament light chain (NfL) level in the interstitial fluid following axonal damage is known to be reflected in the easily accessible serum and predestinates this parameter for clinical investigations in search for a biomarker of cognitive deficits. Sixteen depressive patients aged ≥ 60 years were recruited. For comparison, nine cognitively healthy individuals and eight patients with dementia were included in the study. At baseline, venous blood draws were performed in all participants and serum NfL measurements were carried-out. NfL was able to predict a consecutive dementia diagnosis after remission of depressive symptoms. Despite the relatively small number of patients included in this study, we found statistically significant changes in serum NfL levels between the groups that speak in favor of this - admittedly unspecific - biomarker. The fact that serum NfL changes could predict a consecutive dementia diagnosis after remission of depressive symptoms is of clinical importance: It facilitates an earlier diagnosis and more targeted therapy for the patients with affective and cognitive deficits.