Prevent Memory Loss by Socialising

Strong social ties may preserve memory in old age, according to a new study conducted at the Ohio State University.

Recent statistics show that over 2 million people aged 75 and over live alone in England. And more than 1 million senior citizens say they have gone more than a month without speaking to friends, neighbours, or family members. So how does this isolation impact our brains?

Researchers at the Ohio State University in the United States, lead by Liz Kirby, conducted a study¹ to explore the relationship between socialization and cognitive health, specifically in the elderly.

"We know that in humans there's a strong correlation between cognitive health and social connections,” explains Kirby. “But we don't know if it's having a group of friends that's protecting people, or if it's that people with declining brain health withdraw from their human connections."

To understand this relationship, Kirby and her team turned to mice. The animals used in the experiments were aged between 15 and 18 months, which coincides with the onset of significant decline in memory in these rodents. "It's like mouse post-retirement age,” said Kirby.

Over the course of 3 months, the mice were either housed in pairs or in groups of 7. The pairs of mice simulated elderly couples, while the groups of 7 simulated communities.

Each mouse was placed in a chamber that contained two toys. To test the animal’s memory capabilities, the researchers moved one toy and assessed the reactions of the mice. Previous studies have shown that mice in good cognitive health tend to investigate an object that has been moved as a sign that they remembered the original location of the object.

Overall, the mice that lived in groups were more likely to investigate the relocated toy while ignoring other objects that have not been moved. Meanwhile, most of the mice that lived in pairs did not notice the relocated toy at all.

In another memory test, the mice were placed on a round table with many holes connected to a maze. Some of the holes led to escape routes while others were dead ends.

Over the course of several trials, the mice that lived in groups searched for the escape routes systematically. Researchers noticed that the mice tended to immediately revisit the holes that were escape routes in previous trials, meaning they relied on memory.

On the other hand, the mice that lived in pairs did not show a reliance on memory. Instead, throughout the trials, the paired mice would search for an escape route in a random manner, but would do so faster with each trial.

Kirby compared this method to “walking as quickly as possible through each row of a parking lot to look for your car rather than trying to remember where your car actually is and walk to that spot.” This erratic search method requires little brain power, and does not engage the hippocampus.

The hippocampus is a region in the brain that is responsible for long-term memory. Brain functions of the hippocampus are known to decline with age in both mice and humans. How can we see this decline?

At the end of the experiment, the researchers analyzed the brain tissue of each mouse. There was no evidence of new neuron growth in the hippocampus of any of the mice. Interestingly enough, the paired mice showed much more brain inflammation than the grouped mice, which is physical evidence of crumbling cognitive health. So what does this mean for people?

“Dealing with people every day puts a huge amount of cognitive load on the brain. This cognitive load is mental exercise, and is what helps keep your brain healthy,” explained Kirby.

It is suggested that the best way to engage in mental exercise is by living in a community, especially as you age. Kirby offered this advice, “If you’re making a choice about where to live, choose a living situation where you’ll be able to maintain contact, even as your mobility decreases.”