Andrea Cagan awoke on her 50th birthday as lonely as she’d ever been. She wanted a man, but none were calling. So Cagan, a glowing ex-ballerina, decided to concentrate on her female friends.She now speaks daily long-distance on the phone with her BGF. “We don’t lie in bed and hug or kiss like a romantic couple (I’m not a lesbian and neither is she), but we giggle and love each other and it fills me up,” she writes in “Sixty and Single,” one of two dozen essays in the just-published collection, “Live and Let Love: Notes from Extraordinary Women on the Layers, The Laughter, and the Litter of Love,” edited by Andrea Buchanan.QUIZ: Your Humor Style“Listen up, ladies. I am single and happy,” says Cagan. Scientists agree: Her well-being doesn’t depend on a mate. And in fact, chatting can save your life.Loneliness is Deadly. Friends, family, neighbors and colleagues increase our longevity. Researchers at Brigham Young University studied a sample of healthy adults over a 7.5-year period and reported that those with meaningful relationships had a 50 percent higher survival rate. They also found that isolation is about as dangerous as alcoholism or smoking 15 cigarettes a day.MORE: Why We Crave Comfort Foods When We’re LonelyIf you must choose, see friends over trips to the gym. Having few or insufficient social relationships may be as or more harmful than other serious health problems, including obesity. That conclusion came from a review that compared all-cause mortality rates against the social habits of more than 300,000 people in 148 studies, and is possibly a “conservative estimate,” underestimating the true impact, writes lead author Julianne Holt-Lunstad.Loneliness depletes the body in a process akin to “premature aging,” University of Chicago psychologist John Cacioppo wrote in his groundbreaking 2008 book, “Loneliness.” Cacioppo outfitted people with beepers that chirped throughout the day, prompting them to answer questions related to loneliness—while biosensors at their hips measured their cardiovascular status. He tested both college students and a group of people ranging in age from about 50 to 70, who participated over five years. Lonely people in both age groups rated their stresses as more severe and had poorer social interactions.QUIZ: What’s Your Attachment Style?In a separate study of older adults, the lonely ones showed higher traces of stress hormones, as well as long-term changes in the circulation of cortisol, the body’s stress regulator.A strong core relationship—not necessarily a marriage—causes blood pressure to dip more significantly while you sleep, says Holt-Lunstad, lowering your risk of cardiovascular disease. Even just the fear of isolation can hurt you; other research has found that people who are afraid of being alone in life do worse on tests of logical reasoning.There’s no need to feel ashamed of loneliness. Human beings are physiologically wired for more sociability and intimacy than modern life in the United States easily provides, Cacioppo and others say, while surveys show a steady decline in the number of reported confidantes.MORE: Relationships as RegulatorsWith fewer other sources of love or ordinary connection, a romance may take on more weight. And it’s human nature to want a close sexual partner. “Wanting to be in a romantic relationship is positive and normal,” says psychologist Arthur Aron, who studies romantic love at the State University of New York at Stony Brook. “It’s also not a bad sign if you’re unhappy you’re not in one.”A Many Splendored Thing. A happy marriage brings a cascade of health benefits. Besides companionship, it can boost self-esteem and expand your interests, opportunities and social world. For some, it provides practical benefits like health insurance and more financial security, which are associated with better health. Married people tend to encourage habits in each other, both healthy and unhealthy, and are less likely to drink excessively (maybe because they spend less time in singles bars!).Sex may even be a beauty treatment. According to “RealAge Makeover” by YouBeauty.com co-founder Dr. Michael Roizen, having safe, loving sex twice a week can make you 1.6 years younger—and daily sex may make you up to 8 years younger. For women, the quality of sex (versus the frequency for men) may be a better predictor of youth. Consider headaches a reason to make love, rather than an excuse to roll over: The increase in endorphins and corticosteroids during arousal and orgasm is analgesic.MORE: How Women Work When it Comes to Sex“Regular exposure to a loving partner has extraordinary effects on health and well-being,” says behavioral endocrinologist Winnifred Cutler. Her research has showed that women who have intercourse at least weekly (except during their period) cycle more regularly than other women, and circulate about twice as much estrogen, which helps make hair shiny and skin supple. They also age slower, have fewer hot flashes during menopause and have better circulation. Another benefit of sex is that it strengthens the muscles of the pelvic floor that stem the flow of urine. As women age, they need to keep these strong to avoid incontinence. The same muscles are exercised during intercourse. As with all muscle-building programs, you need to keep at it!The goal of creating a lasting, passionate partnership doesn’t mean you can afford not to pursue other avenues to happiness. As Stephanie Coontz, a prominent historian of American marriage, puts it, “People get the most out of health clubs if they already have a level of fitness. In the same way, if you’ve already developed your own interests, identity, social connections and skills, the more you’ll get out of marriage.”MORE: The Health Benefits of Marriage“And just like joining a health club doesn’t guarantee you’ll get fit, getting married doesn’t mean you’ll necessarily find fulfillment or happiness. You need to find activities that are meaningful and healthy, whether you marry or not. If you do, you’ll have a more successful marriage,” she said.Love Hurts. When marriage turns hostile, the health benefits dwindle or reverse. Conflict in any close relationship raises blood pressure for women and men, especially if they’re fighting with a spouse, Holt-Lunstad reports. In fact, Holt-Lunstad concluded that single people had lower nocturnal blood pressure than the unhappily married, suggesting that having positive, core relationships may be more important than marital status.In another study, researchers fit 42 couples with small suction devices that created eight tiny blisters on their arms. Hostile couples healed 40 percent slower than harmonious couples, taking roughly two days longer to heal.Being rejected in love is literally like experiencing physical pain for our bodies, which is one reason it is a frequent cause of depression and suicide. Divorce is a health risk: A 2009 study in the Journal of Health and Social Behavior found that divorce predicted poorer health at mid-life, even if the person remarried. More specifically, chronic conditions were worse among all divorced people, while depressive symptoms were only worse among those who never remarried.Perception Counts. What matters is that you perceive a core relationship as happy and stable, Holt-Lunstad found, not how or how much the other person actually provides support. Cacioppo also reports that people who are married and sharing a bed are at risk for poor sleep if they feel isolated from each other.How you perceive a relationship may have a lot to do with your childhood experiences, which shape the way you relate to others as an adult. About 10 percent of the population has trouble feeling really satisfied or safe in a love relationship, Aron says.How to Hit the Jackpot. If you’re wondering if you’ve waited too long to marry, it’s worth noting that the age of marriage has gone up. Plus, more educated women are actually more likely to get married than their less educated peers. According to population survey data, “A never-married 30-year-old woman with an advanced degree has a 75 percent chance of walking down the aisle by age 40,” says Christine Whelan, author of “Marry Smart: The Intelligent Woman’s Guide to True Love.” “We’re getting married older—and wiser.“MORE: Mindfulness and AgingAron’s research suggests you don’t need to hold out for perfection, or that head-in-the clouds feeling. “There’s no evidence for soulmates,” he says. “People who are intensely in love in the beginning are slightly more likely to have a good relationship. But only slightly. Talk to anyone in India and they will tell you that people can fall in love later on. It’s a romantic ideal there.“The ingredients for good marriages, Aron says, are reasonable mental health, absence of serious stress and good communication skills. Being able to talk is as important as mental health. “A happy couple’s happiness can deteriorate quickly,” he says, if they communicate badly, “while people who may start off less happy will get happier if the couple practices good communication skills.”You also need to make sure you aren’t bored. In a 2009 study with 123 couples, Tsapelas, Aron and Orbuch found that spouses who said that their relationship was “in a rut” were unhappy with the marriage nine years later, even if there wasn’t a lot of tension.On the other end of the scale, as many as 10 percent of couples are intensely in love even after many years, Aron says. When he put such couples in a brain scanner, “They looked like people who had just fallen in love. They told us that they drive their friends crazy because they can’t keep their hands off each other.” Keep passions high by going on adventures, ideally on a once-a-week date, Aron says. “Go canoeing. My wife and I might say, ‘Why not stop in a bar and hang out, because we haven’t done that for years.’ ”MORE: One Easy Fix to Help Save Your MarriageJust remember that if you don’t hit the jackpot, simple touch can go a long way. Hugging and holding hands release the hormone oxytocin, which helps reduce blood pressure, improves mood and increases tolerance for pain.Cecilia, a Swedish advertising executive, loves to hug her small son. Her interest in men has waned since she became a mother. “It’s really liberating,” she says. “I have my son and that is really what matters to me. I don’t think I’ll look for another relationship for a very, very long time—if ever. Still in my heart I hope I can meet someone that I will have a really deep connection with.”Whether you’re in a committed couple relationship or not, make the most of the relationships you have for a long, healthy life.