Social isolation may be associated with poor health consequences, including heart disease, researchers say.

People with atherosclerosis, or hardening of the arteries, and who live alone may be at higher risk of dying than those living with others, an international study finds.

Learning more about how living alone affects health is important, considering that about one in seven American adults live alone. People in both developed and developing countries increasingly live apart from friends and family and communicate and work remotely.

In Monday’s online issue of the Archives of Internal Medicine, Dr. Jacob Udell of Brigham and Women's Hospital and Harvard Medical School in Boston and his co-authors said living alone was associated with four-year mortality (14.1 per cent vs. 11.1 per cent) and cardiovascular death (8.6 per cent vs. 6.8 per cent) compared with those not living alone.

Living alone was riskier among those aged 45 to 65, but not those 66 or older, the researchers found.

"Living alone may be a marker of a stressful situation, such as social isolation due to work or personal reasons, which can influence biological effects on the cardiovascular system," Udell said.

"Also, patients who live alone may delay seeking medical attention for concerning symptoms, which can increase their risk of dying from a heart attack or stroke," he added in a release.

The study looked at 44,573 people in North America, Europe, Japan, Middle East, Latin America and Asia. Of these, 19 per cent were living alone.

Participants either had atherothrombosis such as heart disease, angina and stroke, or had at least three risk factors for cardiovascular disease.

Social factors can undermine health

The researchers said the findings should encourage doctors to ask patients with cardiovascular disease if they live alone.

In a second study appearing in the same issue, Dr. Carla Perissinotto, of the University of California, San Francisco, found that loneliness was associated with an increased risk of death during the study's six-year followup period.

Older people who said they felt lonely tended to have more difficulty taking care of themselves, which could increase the risk of dying from any cause, after considering depression.

"Loneliness is a negative feeling that would be worth addressing even if the condition had no health implications," Emily Bucholz of Yale University in New Haven, Conn., concluded in a journal commentary accompanying the research papers.

"Nevertheless, with regard to health implications, scientists examining social support should build on studies such as those published in this issue and be challenged to investigate mechanisms as well as practical interventions that can be used to address the social factors that undermine health."

Udell's research was supported by Sanofi Aventis, Bristol-Myers Squibb, Waksman Foundation in Tokyo, Canadian Institutes for Health Research and the Canadian Foundation for Women's Health. Perissinotto's study was funded by the U.S. National Institute on Aging.

SEE: Five causes of loneliness, from Delia Lloyd:
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  • 1. Aging

    Sure, depression is common in old age, and <a href="" target="_blank">people are living longer</a> than ever before. But <a href="" target="_blank">the role of the elderly</a> within communities is also shifting, from traditional societies where the elderly held a hallowed place as the repository of community customs, history and stories, to post-industrial societies where this guidance function is much less valued. As this sociological shift takes place, older people risk feeling marginalized from their families and neighborhoods, particularly if they end up in nursing homes. <em>Flickr photo by <a href="" target="_hplink">Horia Varlan</a></em>

  • 2. Death And Divorce

    Writing about the loneliness epidemic, one national columnist talked about the "three Ds": <a href="" target="_blank">death, divorce and delayed marriage</a>. It's not hard to see why the death of a spouse would trigger a feeling of loneliness. <a href="" target="_blank">Jane E. Brody had a lovely meditation</a> on this topic in the <em>New York Times</em> not long ago. The divorce point is more interesting. We know, for example, that <a href=",8599,2033283,00.html" target="_blank">online dating</a> has seen its highest growth rate among baby boomers. But <a href="" target="_blank">all that dating</a> doesn't necessarily translate into feeling less lonely. Sometimes it just reinforces it, as people bounce from one partner to another. <em>Flickr photo by <a href="" target="_hplink">firemedic58</a></em>

  • 3. Social Media

    Which brings us to social media. The central thesis of <em>The Atlantic</em> article I referenced earlier is that even as <a href="" target="_blank">we become ever more connected</a> as a society digitally, we are becoming less immersed in real-life social ties. This is not a new thesis, and as someone who spends a lot of time online I can readily attest to its accuracy. What's interesting about the article is that it looks very closely at Facebook and references research suggesting that while "active" interaction on Facebook -- e.g., making a comment on someone's status update, sending a private message -- tends to make people feel less lonely, just passively scrolling through other people's feeds and hitting the odd "like" button can make you feel more lonely. An earlier study offers some insight into this finding: Because we are <a href="" target="_blank">psychologically predisposed</a> to overestimate other people's happiness, when we see the invariably upbeat, relentlessly witty and sometimes just plain gushing status updates that pretty much define Facebook, it makes us feel worse about ourselves.

  • 4. Commuting

    Here's a factor I hadn't considered, but which makes perfect sense. According to Robert Putnam, the famed Harvard political scientist and author of <a href="" target="_blank"><em>Bowling Alone</em></a>, <a href="" target="_blank">long commuting times</a> are one of the most robust predictors of social isolation. Specifically, every 10 minutes spent commuting results in 10 percent fewer "social connections." And those social connections tend to make us feel happy and fulfilled. <em>Flickr photo by <a href="" target="_hplink">Richard Masoner</a></em>

  • 5. Genetics

    There is also likely a genetic component to loneliness. One <a href="" target="_blank">survey of loneliness among twins </a>showed much less variability in the self-reporting of loneliness among identical twins than among fraternal ones. There's also been a lot of fascinating research coming out of The University of Chicago about the way in which loneliness shapes brain development and vice versa, suggesting <a href="" target="_blank">a neural mechanism in explaining loneliness</a>. <em>Flickr photo by <a href="" target="_hplink">Sheryl</a></em>