'I'm not going to pay someone to be my friend," clients often tell Paul Blom.

Blom doesn't argue. His Bloomington-based company Right at Home provides various services for older people, including housekeeping and meal preparation. Simple companionship, though also available, is optional.

But often, clients wind up appreciating personal interaction more than they expected. When Blom calls clients later to check their satisfaction with the care provider's services, "A lot of them say, 'I love it when there's extra time at the end, when all the things I want to do are done, because then we just sit and visit and have a cup of coffee or play cards,'" he said.

Not everyone wants to admit it, but enjoying another person's company "is a big deal," Blom said.

A bigger deal than most people realize. A lack of social engagement doesn't just put a damper on your Saturday nights — it can actually harm you physically.

Loneliness is as bad for your health as smoking cigarettes, according to a large 2010 study. Psychologists at Brigham Young University analyzed 148 smaller studies involving more than 300,000 people and concluded that loneliness can increase the chance of death as much as smoking, and more than physical inactivity or obesity.

In another study, University of California geriatricians followed people over age 60 for six years, concluding in 2012 that "loneliness was a predictor of functional decline and death." Earlier this year, the British government launched an effort to evaluate loneliness in the population, amid concerns that it's a growing problem that will stress the country's health service. It has been linked to heart disease, high blood pressure, dementia, depression and a weakened immune system.

But the physical risks are not widely recognized by health organizations or the public, the Brigham Young authors wrote.

Blom has noticed them, though, among his clients.

"People who are disengaged socially, either because of family dysfunction or whatever it is, they simply don't do as well physically," Blom said. "I've got clients who've hit 100 and better and are doing great, because they're socially engaged."

More than a third of respondents in a 2010 AARP survey described themselves as chronically lonely. Retired people, somewhat counterintuitively, were slightly less lonely than those still working. But those who kept in touch with former co-workers were far less lonely than those who did not.

"'I don't miss the work, but I miss the people I used to work with" — that's what I hear all the time," said Merrie J. Kaas, specialty director of the psychiatric mental health nurse practitioner program at the University of Minnesota.

Scientists are still trying to figure out why social engagement would affect physical health. One theory is that we're hard-wired to depend on others. Groups offered protection, after all, in the dangerous circumstances under which early humans evolved.

"As a social species, humans rely on a safe, secure social surround to survive and thrive," wrote the authors of a 2010 University of Chicago study. Lacking that may "heighten feelings of vulnerability" and create a sense of threat which, among other things, can diminish sleep quality.

But the relationship between loneliness and health problems is complex, with the causes and effects potentially flowing both ways. For example, if loneliness can trigger depression, depression can aggravate loneliness. Kaas works with depressed clients who would benefit from getting together with others but "don't have the energy or motivation to be engaged."

Friends and family can provide overtly practical benefits, such as helping deal with health impairment. People who are socially isolated, research suggests, are more likely to enter nursing homes.

"One of the things you see clearly is the need for older persons with chronic illnesses or disabilities to rely on families for ongoing support," said Joseph Gaugler, an associate professor at the U's School of Nursing. "We certainly know that if they don't have available family, they're at greater risk for negative outcomes."

Other people also provide intellectual stimulation. Gaugler said the most beneficial activities probably combine social interaction and intellectual challenge: "Staying active in the workplace in some way, volunteering in community groups and causes, joining clubs, square dancing, trying to learn a second language, learning to play chess."

Without companionship, even eating may be more hazardous, Blom pointed out.

"Elderly people who isolate and live alone are much quicker to become malnourished and dehydrated, because for most of our lives eating is a social thing," he said. "Pretty soon you're popping a frozen dinner in the oven every day, with sodium and carbohydrates at levels you really shouldn't be consuming."