Old brains can still grow cells like young ones, study finds

Old age may weigh on our bodies, but not necessarily on our brains. Research published today shows for the first time that healthy older men and women are capable of generating just as many new neurons as younger people.

Previous research has suggested that humans stop growing new brain cells later in life, as is the case in rodents and non-human primates. It had been thought that waning production of neurons in the hippocampus – a part of the brain linked to emotion and cognition – was part of the ageing process.

A study in the journal Cell Stem Cell rebuts that conclusion, presenting evidence that people reaching their 80s produce comparable levels of neurons to 14-year-olds. “We found that older people have [a] similar ability to make thousands of hippocampal new neurons from progenitor cells as younger people do,” says lead author Maura Boldrini, associate professor of neurobiology at Columbia University. “We also found equivalent volumes of the hippocampus across ages.”

As part of the study, researchers from Columbia University and New York State Psychiatric Institute autopsied hippocampi from 28 individuals aged 14-79, who had all died suddenly and been mentally healthy up to their death. The scientists analysed each hippocampus, and found – as they describe in their paper – “similar numbers of intermediate neural progenitors and thousands of immature neurons”.

“These neurons might be important in humans for our abilities to transmit complex information to future generations, and to sustain our emotionally guided behaviour, as well as for integrating complex memories and information like humans do,” Boldrini tells Alphr. “This also means that through healthy lifestyle, enriched environment, social interactions, and exercise, we can keep these neurons healthy and functioning, and sustain healthy ageing.”

The results suggest that older people may be more cognitively and emotionally resilient than has been assumed, although not everything was found to be consistent across the different age groups. Boldrini notes that “older individuals had less vascularisation and maybe less ability of new neurons to make connections,” suggesting that even if new neurons are produced, there may be less cell-to-cell connectivity made in the brain.  

Older people also have an “exhausted quiescent progenitor pool”, meaning aged brains have fewer progenitor cells that are able to differentiate and self-renew. Further research by the team will aim to look closely at how these factors interact with new neurons being produced, and whether exercise, diet and medication can offset waning connectivity in the brain. You know the old saying: you’re only as old as the neuroplasticity in your hippocampus makes you think you are.  

As well as potentially changing the way we think about the health of older brains, the research by Boldrini and her team could pave the way for new treatments for degenerative diseases like Alzheimer’s.

“We are interested in understanding how neuron proliferation, maturation and survival are regulated by trophic factors, transcription factors, hormones and other molecules, and in doing that we could find treatments for cognitive impairment/dementia,” she tells Alphr.

“We would be also interested in comparing these findings obtained in healthy ageing individuals, with possible findings we could obtain studying people with cognitive impairment or Alzheimer’s or vascular dementia, and understand what is different in this conditions.”