Friends With Benefits: Being Highly Social Cuts Dementia Risk by 70%

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Yet more evidence that friends and family are the best medicine: a new study finds that the most social seniors had a 70% reduction in the rate of cognitive decline, compared with their least social peers.

The study followed 1,138 people for an average of five years. None of the participants, whose average age was 79.6, had dementia at the start of the study. Because the study followed people over time, starting from when they were mentally healthy, the findings shed light on the question of whether it’s early signs of dementia that cause social isolation, or whether it’s a lack of sociability that causes a greater risk of mental decline.

“The problem was what came first, the chicken or the egg,” says lead author Bryan James, a postdoctoral fellow at the Rush Alzheimer’s Disease Center in Chicago. “We followed people for up to 12 to 14 years so we were able to look at not just changes in cognition but changes in social activity. That way we were able to see which preceded the other.”

(More on Time.com: Feeling Alone Together: How Loneliness Spreads)

To measure participants’ levels of social activity, the researchers used a questionnaire that inquired about things like visits to relatives and friends; participation in activities such as bingo, sporting events, restaurant-going or volunteering; attendance at religious ceremonies; and active membership in groups like the Knights of Columbus. Responses to the questionnaire produced a numerical score of social activity.

Each one-point increase on the social activity score was linked to a 47% drop in the rate of decline in cognitive function, the researchers found. An earlier study of the same group of elderly participants by the same researchers also found that each one-point increase in sociability reduced the risk of becoming physically disabled by 43%. “Not only is socializing linked to mental and thinking ability, it’s also about how well you live independently,” says James.

(More on TIME.com: Friends Are Key to Health and Long Life)

The researchers controlled for factors like personality and the size of participants’ social networks and still found a large effect of actual social activity.

Previous studies have found that severe social isolation is at least as deadly as smoking — doubling your risk of early death — and that those with more and higher-quality relationships are at lower risk for a host of illnesses including heart disease and stroke. In fact, having strong friendships or family connections reduces your risk of early death more than exercising or avoiding obesity does — and as a bonus for most of us, it’s more fun and takes less willpower.

So why is interaction with friends and family so healing? Our stress response is intimately linked with our social connections — that’s why holding Mom’s hand, even as an adult, can lower blood pressure for most people, and why infants raised with minimal human contact are at many times the risk of childhood death as those with loving families. Lack of social contact is stressful for all social animals, and high chronic stress increases risk of cardiovascular disease, some cancers, obesity, all mental illnesses and addictions.

“Socializing relieves stress, and there’s a huge connection between stress and problems with the brain as we get older,” says James.

(More on Time.com: The Soothing Effect of Mom’s Voice)

The evolution of the human brain seems to have been driven by the complexity of our social world. Our social life is the most complex of any primate and involves greater numbers of relationships. Indeed, in primates, the number of members involved in social groups is linked with bigger neocortexes — the region of the brain that is associated with the highest cognitive functions and is, in humans, most highly developed.

“Our brains may be evolved for knowing about 150 people,” says James. “If you only interact with one or two people, it may not be what we evolved to do.”

It’s not surprising, then, that socializing would reduce dementia risk: our brains were designed for managing relationships. And with brains, as with muscles, the same advice applies — use it or lose it.

The research was published in the Journal of the International Neuropsychological Society.

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