Research by an American professor of psychology, John Cacioppo, suggests that extreme loneliness can increase the chances of premature death by 14 per cent. Chronic loneliness is twice as likely as obesity to lead to an early death and has almost the same impact as socio-economic disadvantage.

"People may think of feeling lonely as a sad condition but ... finding oneself on the social perimeter is not just sad, but also dangerous," says Cacioppo.

People who feel isolated are more likely to sleep badly, have high blood pressure, poor immune resistance and spikes in the stress hormone cortisol, all of which can lead to a shorter life. They often live in a constant state of high alert, suffer anxiety and depression, and have a poorer sense of overall well-being. By contrast, those with satisfying relationships are more resilient and better able to overcome stress.

Cacioppo says the research highlights the need for people to stay connected, especially as they grow older and move from work into retirement.

"Retiring to Florida to live in a warmer climate among strangers isn't necessarily a good idea if you are disconnected from the people who mean the most to you," he told this year's annual meeting of the American Association for the Advancement of Science. "People have to think about how to protect themselves from depression, low subjective well-being and early mortality."

A 2011 report by the Australian Housing and Urban Research Institute found that 35 per cent of men and 29 per cent of women reported loneliness as a problem in their lives. According to the Australian Bureau of Statistics (ABS), people living alone, single parents, new migrants and refugees are most at risk.

The Australia Institute's David Baker says that in any given year over the past decade, one in 10 Australians has felt lonely. But over the course of that decade as a whole, 30 per cent of us have been lonely. "It's affecting more people in the longer term," says Baker.

Men suffer more from loneliness than women, and are more likely to be the affected partner in couples without children. But in couples with children, women are more commonly affected. And while not all people who live alone are lonely, it is a factor. This is alarming, given that the ABS predicts the number of people living solo will rise from two to three million in the next 20 years.

"We need to look at ways people can reconnect with the community," says Baker. "Programs such as men's sheds may be effective at addressing the broader issue."

Experts agree that the number of Facebook friends or Twitter followers you have does not correlate to real-time connectedness. Indeed, feeling part of a community is as important as staying connected to family and friends.

Sydney clinical psychologist Dr Cindy Nour suggests a friendship drive every few months. "Ring a friend, and if they don't answer, call the next person on the list," she says.

If old friendships are becoming stale, says Nour, make new connections via an interest group, club or online networking site such as meetup.com. For some, just going to a cafe and sitting among others can help create a sense of belonging, while people who work at home should consider renting shared office space.

"For most people, loneliness is a transient emotion," says Nour. "It's one of those emotions that comes and goes, and it can be easily managed. You've just got to find some connection."

Professor Cacioppo identifies a three-pronged plan to end chronic loneliness. First, have intimate connections with people who affirm you. Next, seek out face-to-face relationships with people whose company you enjoy. Finally, find a "collective" - a group or a community that you identify with.

"If obstacles to connectedness seem insurmountable, consider volunteering," he suggests. "And don't wait. The next time you feel alienated, isolated or excluded, respond as you would to hunger, thirst or pain. Get connected."