Blood biomarker study points to new aging tool across species
Bottom line
Researchers at the German Center for Neurodegenerative Diseases and the Hertie Institute for Clinical Brain Research reported that neurofilament light chain, or NfL, a blood marker already used in human neurodegeneration research, may also help track aging across species. In a PLOS Biology study published in February 2026, the team analyzed blood samples from 862 animals across 57 species and found that NfL increased with age in mice, cats, dogs, and horses, with trajectories that resembled those seen in humans. In a longitudinal mouse cohort, faster increases in NfL were also linked to shorter remaining lifespan. The researchers say the marker could eventually help assess biological age and mortality risk in animals. (eurekalert.org)
Why it matters: For veterinary professionals, the finding adds to a growing body of evidence that blood-based neurologic biomarkers may have practical value beyond research settings. Prior canine studies have already linked circulating NfL to neurodegeneration and cognitive dysfunction, and recent veterinary literature has suggested these biomarkers could complement clinical assessment and imaging, even though they remain only marginally used in practice today. The new cross-species data broadens that conversation, especially for senior pet care, comparative medicine, and future monitoring of aging interventions, but the authors also note an important limitation: many samples came from diagnostic labs, so undetected illness could have influenced NfL values. (pmc.ncbi.nlm.nih.gov)
What to watch: Watch for follow-up work that establishes species-specific reference ranges, validates the marker in healthier prospective cohorts, and clarifies whether NfL can move from a promising research tool into routine veterinary use. (pmc.ncbi.nlm.nih.gov)
A blood biomarker better known from human dementia and neurodegeneration research may have broader veterinary relevance than previously thought. In a February 20, 2026 announcement tied to a new PLOS Biology paper, researchers from the German Center for Neurodegenerative Diseases and the Hertie Institute for Clinical Brain Research said neurofilament light chain, or NfL, is detectable across a wide range of animals and rises with age in mice, cats, dogs, and horses. Their conclusion: NfL may serve as a cross-species biomarker for biological aging and, potentially, mortality risk. (eurekalert.org)
The work builds on a well-established human literature. In people, NfL is used as a marker of neuroaxonal injury and is studied in conditions including Alzheimer’s disease, ALS, Parkinson’s disease, and multiple sclerosis. Human studies have also shown that NfL rises with normal aging and can predict mortality in older adults. Veterinary researchers have already been exploring that translational bridge, especially in dogs, where plasma or serum NfL has been studied in aging, epilepsy, and cognitive dysfunction. (nature.com)
In the new study, investigators measured NfL in blood from 862 animals representing 57 species, drawing on samples from veterinary diagnostic laboratories, a zoo biobank, and academic sources. They excluded samples with known neural injury, then compared age patterns across species. The clearest age-linked findings came from mice, cats, dogs, and horses, where NfL rose nonlinearly over the lifespan, with a relatively slow increase through adulthood and a steeper rise late in life. The paper reports roughly 3-fold age-related increases in horses, 14-fold increases in mice and dogs, and a 36-fold increase in cats. NfL was also detected in many other mammals, plus some birds and reptiles, although the authors cautioned that non-mammalian findings may be limited by assay sensitivity and possible false positives. (pmc.ncbi.nlm.nih.gov)
One of the more notable findings came from the mouse data. In 44 aging C57BL/6J mice sampled longitudinally, a faster month-to-month rise in NfL was associated with shorter remaining lifespan. The authors reported that each standard deviation increase in the NfL slope was linked to a 73.5% higher mortality risk, supporting the idea that the marker may reflect biological aging rather than only overt neurodegenerative disease. Still, the study has caveats. Because many animal samples came from diagnostic labs, some animals may have had unrecognized health problems that affected NfL levels, and the mortality analysis was limited to aged mice under laboratory conditions. (pmc.ncbi.nlm.nih.gov)
That caution matters in a veterinary context, where enthusiasm for blood-based biomarkers is growing, but clinical adoption remains early. A 2024 Scientific Reports paper on canine neurologic disorders noted that fluid biomarkers such as NfL could improve diagnostic accuracy when combined with clinical assessment and imaging, yet are still used only marginally in veterinary medicine. Separate canine studies have found that NfL rises in dogs with neurodegenerative disease and may help diagnose or stage canine cognitive dysfunction syndrome, reinforcing the idea that the marker is already relevant to companion animal neurology, even before this broader cross-species paper. (nature.com)
Why it matters: For veterinarians, the immediate takeaway isn’t that NfL is ready for routine screening of every senior patient. It’s that a biomarker once viewed mainly through the lens of human dementia research is starting to look like a more general measure of neural aging across species. That could eventually support earlier recognition of neurologic decline, better stratification of senior pets in clinical studies, and more objective monitoring of anti-aging or neuroprotective interventions. It may also strengthen comparative medicine efforts, especially as canine cognitive dysfunction and other age-related neurologic conditions are increasingly framed as translational models for human disease. (pmc.ncbi.nlm.nih.gov)
There’s also a practical challenge ahead. For NfL to become useful in everyday veterinary medicine, the field will need species-specific reference intervals, better control for comorbidities, and prospective studies in well-characterized populations rather than convenience samples from referral or diagnostic settings. Breed, body size, life stage, and concurrent disease are all likely to matter, particularly in dogs. The current study itself notes that body size and lifespan are intertwined, making cross-species interpretation difficult. (pmc.ncbi.nlm.nih.gov)
What to watch: The next phase will likely focus on validation, including prospective studies in companion animals, assay standardization, and efforts to determine whether NfL can move from a promising comparative biomarker to a clinically actionable tool for senior pet care and veterinary neurology. (pmc.ncbi.nlm.nih.gov)