Key TakeawaysThe brains of newborn babies and seniors with Alzheimer’s disease share a common traitBoth have high levels of tau, a brain protein that forms toxic tangles in Alzheimer’s patientsThis suggests humans have built-in protection against tau that fades over time.THURSDAY, Aug. 21, 2025 (HealthDay News) — The brains of newborns have a surprising trait in common with adults who’ve developed Alzheimer’s disease, a recent study says.Both have elevated blood levels of a well-known biomarker for Alzheimer’s – a protein called phosphorylated tau, researchers reported recently in the journal Brain Communications.Tau is associated with the amyloid beta plaques and tau tangles that riddle the brains of people with Alzheimer’s, researchers noted.But in newborns, this tau surge appears to support healthy brain development, helping neurons grow and form connections with other neurons, researchers found.This hints that human brains might have built-in protection against tau’s potentially damaging effects, so newborns can tolerate and even benefit from heavy levels of tau without triggering Alzheimer’s-like damage, researchers said.“We believe that understanding how this natural protection works — and why we lose it as we age — could offer a roadmap for new treatments,” lead investigator Fernando Gonzalez-Ortiz, a doctoral student at the University of Gothenburg in Sweden, said in a news release.“If we can learn how the newborn brain keeps tau in check, we might one day mimic those processes to slow or stop Alzheimer’s in its tracks,” he added.For the new study, researchers compared blood levels of a type of tau called p-tau217 in more than 400 people, including newborns, teenagers, young adults, seniors and people with either mild cognitive impairment or Alzheimer’s.Blood testing for p-tau217 recently received FDA approval for use in diagnosing Alzheimer’s disease, researchers noted.Results showed that newborns had the highest levels of p-tau217 — even higher than those found in diagnosed Alzheimer’s patients, researchers said.The levels were particularly elevated in premature babies, and started to decrease over the first few months of life until they settled to levels typically found in young adults.Researchers also found that p-tau217 levels were closely linked to how early babies were born. The earlier the birth, the higher the baby’s tau levels, suggesting that it serves a role supporting rapid brain growth under challenging developmental conditions.Future studies should explore the protective mechanisms that protect babies’ brains from the development of tau tangles found in Alzheimer’s patients, researchers said.More informationThe Alzheimer’s Association has more on amyloid beta and tau.SOURCE: University of Gothenburg, news release, June 24, 2025 .What This Means For YouUnderstanding how babies’ brains use tau could help doctors develop treatments for Alzheimer’s disease..Sign up for our weekly HealthDay newsletter