“To understand how and why people may be resistant to developing Alzheimer’s disease, it is important to closely investigate the postmortem brains of superagers,” said lead researcher Tamar Gefen, an assistant professor of psychiatry and behavioural sciences at Northwestern University Feinberg School of Medicine.

“What makes superagers’ brains unique? How can we harness their biologic traits to help elderly stave off Alzheimer’s disease?”

“The remarkable observation that superagers showed larger neurons than their younger peers may imply that large cells were present from birth and are maintained structurally throughout their lives. We conclude that larger neurons are a biological signature of the superaging trajectory.”

To make the discovery, the team examined the brains of six superagers, seven cognitively average elderly individuals, six young individuals and five individuals in the early stages of Alzheimer’s.

They concentrated their studies on the entorhinal cortex as it is one of the first locations to be affected by Alzheimer’s disease. It is made up of six layers of neurons stacked on top of one another. The second of these layers is known to be a particularly important hub that receives information from other memory centres in the brain.

The neurons that make up this second layer were found to be bigger in superagers than in all of the other groups, even those who were 20 to 30 years younger. They were also found to be free from tau tangles.