# Neurofilament light chain may serve as a cross-species blood biomarker to assess aging and predict mortality

## TL;DR

The study finds that neurofilament light chain (NfL) in blood increases with age and predicts mortality in humans and several animal species, suggesting it could be a useful aging biomarker across species.

## Contribution

The study demonstrates that NfL is a conserved blood biomarker of aging and mortality across multiple species, including mice, cats, dogs, and horses.

## Key findings

- NfL levels increase with age in mice, cats, dogs, and horses, similar to humans.
- Higher baseline NfL levels correlate with shorter lifespans across 13 species.
- NfL was detected in blood of 39 mammals and some reptiles and birds, indicating evolutionary conservation.

## Abstract

Blood levels of neurofilament light chain (NfL) increase with age in healthy humans and have been shown to predict all-cause human mortality. To determine whether this relationship is conserved across species, we analyzed NfL in the blood of various animals. We observed age-related increases in NfL levels comparable to those seen in humans in mice, cats, dogs and horses. Longitudinal analysis of NfL trajectories in aged mice demonstrated that a faster rate of NfL increase predicts mortality. When comparing baseline NfL levels across 13 species, we found that those with lower baseline NfL levels tended to have longer lifespans; however, the collinearity between body size and life span complicates the interpretation of this finding. NfL was also robustly detected in blood of 39 additional mammalian species, as well as a few reptiles and birds, consistent with a conserved amino acid sequence of the NfL fragment in blood. Given the growing interest in NfL as a biomarker for neurological health and mortality in humans, our findings suggest that NfL may serve as a cross-species blood biomarker for assessing aging interventions and predicting mortality.

Blood levels of neurofilament light chain (NfL) increase with age in healthy humans and can predict all-cause human mortality, but is this true across species? This study shows that NfL age-related blood levels are comparable across mice, cats, dogs and horses, and may serve as a cross-species biomarker for assessing aging interventions and mortality prediction.