The brain changes associated with Alzheimer’s usually lead to a severe loss of memory and cognitive abilities, but not always.

Now, a new study led by a team at the University of California, San Diego (UCSD) helps explain why.

Based on postmortem brain research, around 20 to 30 percent of older adults are thought to have asymptomatic Alzheimer’s disease (ASYMAD). Their brains have the characteristic buildup of misfolded amyloid-beta and tau proteins, but they show no detrimental mental effects.