Loneliness and the Brain

Our social relationships, from the love and intimacy we share with family to the common courtesies we exchange with strangers, and everything in between, are life itself, as essential as the oxygen we breathe. Our connections to others are a powerful influence on our mental and physical health. People who enjoy strong social relationships live longer, healthier lives, and when they do get sick, they fare better. Research shows, for example, that having friends is as important for an individual’s overall well-being as eating right, getting enough exercise and not smoking. One study found that even casual friendships with “the more peripheral members of our social networks” carry a definite health benefit. Another linked friendship to greater resistance to the common cold.

The NIH estimates that 24 percent of community-dwelling (not institutionalized) Americans 65 and older can be considered socially isolated. And in a nationally representative study from the University of California, San Francisco, 43 percent of subjects aged 60 and up reported feeling lonely. Thanks in large part to the aging population, loneliness is on the rise in the U.S.

And that trend was made dramatically worse by the pandemic, which was especially tough on seniors. It isolated them at home and in care facilities and prevented them from seeing (and hugging) their children and grandchildren. It cut them off from their friends and the comforting rituals of friendship and forced them to ride out the crisis alone.

People experience loneliness at every stage of life, but as they move through their sixties, they become more vulnerable to its hazards, for a variety of reasons. If they retire, for instance, they may gradually lose contact with their friends and colleagues from work, a common experience that can pack an unexpected emotional wallop. Office relationships, which people tend to take for granted, can’t be easily replaced. Neither can the daily work routine, with its subtle comforts (drinks with co-workers after a busy day), or the sense of being needed, of being part of a group or an organization, of being connected.

On the home front, connections with adult children (and grandchildren) can suffer if they move away for career opportunities. Empty-nesters decide to sell the big house and relocate, only to discover that they miss their old friends, and that meaningful new friendships are a lot harder to come by when you are 70. People become ill or disabled and can’t hang out the way they once did. And then there’s the big blow – a spouse dies. As these normal later-life events reduce the number and quality of a person’s relationships, the risk of loneliness, with its galaxy of dangerous complications, increases.

The loneliness arising from social isolation is a pathological condition that can be clinically diagnosed and has been linked to multiple toxic effects. These include alcoholism, depression, anxiety, suicidal thoughts, aggression, sleep disorders, obesity, hypertension, an increased risk of coronary heart disease and stroke, a compromised immune system and the under-expression of genes involved in the body’s protective anti-inflammatory response. Finally, it tops off that tsunami of morbidity by increasing the risk of premature mortality from all causes (aka, early death) by 26 percent.

Unlike many public health problems, loneliness is an equal opportunity threat that afflicts rich and poor alike. Education level and ethnicity don’t matter, and neither does sex. According to the late John T. Cacioppo, the University of Chicago neuroscientist who pioneered the study of loneliness before his death in 2018, “in industrialized countries, around a third of people are affected by [loneliness], with one person in 12 affected severely, and ... these proportions are increasing.”

Impact on the Brain

For all of its negative effects on bodily health, the true danger of loneliness is its impact on the brain, the way it accelerates cognitive decline in older adults and increases the risk of dementia by around 50 percent. Our brains are what connect us to each other, they are how we know each other, how we experience each other and our shared reality. In the absence of those connections, even their perceived absence, brains can go wrong. Exactly how they go wrong – which structures, networks and cognitive functions are affected by loneliness – is a subject of increasing interest for scientists around the world.

The body of research explicitly linking loneliness to dementia has grown steadily in recent years. One of the striking things about that work is the difference between the normal, passing loneliness we have all felt at various times in our lives and the deep loneliness captured by the scientists. It’s the difference between a sneeze and a heart attack. Consider the people whose isolation is revealed by the heartbreaking 20-question UCLA Loneliness Scale, a common research tool that asks subjects “How often do you feel that there is no one you can turn to?” and “How often do you feel left out?” and “How often do you feel that no one really knows you well?” Reply options are never, rarely, sometimes and always. One important longitudinal study of loneliness and dementia kept it simple with a single yes-or-no question for its 1,905 participants: “Do you often feel lonely?”

The intent of the research is not to evoke the sheer weight of profound loneliness, though it does that quite well, but to explore its causes and effects, what it is and what it isn’t. One important question concerns the concept of reverse causality. To wit: is loneliness a risk factor for dementia or a symptom of dementia. Because dementia develops over a long period of time, it could be that dementia-related declines in language function, for example, might lead some people to withdraw socially and become lonely.

To control for this, studies that followed subjects over long periods of time excluded those who received a dementia diagnosis within the first few years. The largest loneliness/dementia study to date, which followed 12,000 participants over the course of ten years, eliminated anyone diagnosed with dementia within the first six years. When the association between loneliness and dementia persisted in the wake of those exclusions, the researchers concluded that loneliness is a risk factor for dementia, and not just an early symptom.

Social Network, Social Activity

Like Tolstoy’s unhappy families, each lonely person is lonely in their own way. There is no single, widely-used, empirical measure of loneliness. When it comes to assessing social isolation (and perceived social isolation), researchers take different approaches and look at a variety of factors and behaviors. Broadly, these fall into two categories – social network and social activity. For an individual’s social network, the relevant data might include the number of contacts (connections) they have, how often they interact with them, marital status, family size and living arrangement. Social activity might include employment, volunteer work, church attendance, club or group memberships, visits with family and friends, and leisure activity, such as going to museums or out to dinner.

Denied the stimulation of meaningful human contact, people afflicted by loneliness risk leading emotionally and intellectually stunted lives. At a very basic level, many of the steps individuals can take to help maintain their cognitive health as they age, such as learning new skills, staying physically active and keeping a busy schedule, involve other people. For those who lack social relationships, even such simple options may be out of reach. The implications of that for older adults are no small thing. Research shows that even a modest amount of moderate aerobic exercise, for example, is sufficient to improve brain function and reduce the risk of cognitive decline by as much as 40 percent.

In a recent study, however, leading loneliness researcher Louise Hawkley identified a troubling pattern of reduced physical activity among lonely individuals, compared to nonlonely individuals. She described it as an example of “poorer self-regulation when feeling isolated,” noting that the ability to self-regulate “to better meet social standards or personal goals,” is an aspect of executive function.

The Hunt for Answers

The idea that the effects of loneliness on psychological health and well-being may reflect changes in the structural and functional organization of the brain was explored in two recent studies. In one, researchers at Montreal’s McGill University worked with a massive United Kingdom biomedical database that included brain scans and replies to a loneliness survey from 40,000 subjects, ranging in age from 40 to 69. Their findings suggest that loneliness alters a specific brain network known to support memory and imagination, the default mode network ... It seems that, for lonely people, a lack of meaningful social interaction sparks imagination and the desire to reminisce about past social encounters. “We speculate that the associations between the default network and loneliness revealed here reflect increased demands on episodic mental simulation of inner social events in the absence of desired social experience in the external world,” the researchers wrote. To put it another way, lonely people spend a lot of time thinking about times when they weren’t lonely.

Although the integrity of the default mode network may be strengthened by loneliness in adulthood, another study, by a team of German scientists, demonstrates that loneliness may reduce the actual size of brain structures within this network in late life. (Other structures were reduced as well.) This second study, which involved older adults, aged 61 to 82, found that loneliness was associated with a significant reduction in the size of structures that support memory, imagination, and functions for social and emotional processing. The takeaway –maintaining the long-term structural integrity of these regions in late life may depend on continued social interactions that are not available to lonely people.

Living in a big city is no sure guard against loneliness and its effects. But if the answer to social isolation is connecting with other people and keeping busy, New Yorkers have more than eight million possible solutions.