People who survive a heart attack often describe it as a wake-up call. But for a 61-year-old executive I met recently, it was more than that. This man was in the midst of a divorce when he was stricken last spring, and he had fallen out of touch with friends and family members. The executive's doctor, unaware of the strife in his life, counseled him to change his diet, start exercising and quit smoking. He also prescribed drugs to lower cholesterol and blood pressure. It was sound advice, but in combing the medical literature, the patient discovered that he needed to do more. Studies suggested that his risk of dying within six months would be four times greater if he remained depressed and lonely. So he joined a support group and reordered his priorities, placing relationships at the top of the list instead of the bottom. His health has improved steadily since then, and so has his outlook on life. In fact he now describes his heart attack as the best thing that ever happened to him. "Yes, my arteries are more open," he says. "But even more important, I'm more open."

Medicine today focuses primarily on drugs and surgery, genes and germs, microbes and molecules. Yet love and intimacy are at the root of what makes us sick and what makes us well. If a new medication had the same impact, failure to prescribe it would be malpractice. Connections with other people affect not only the quality of our lives but also our survival. Study after study find that people who feel lonely are many times more likely to get cardiovascular disease than those who have a strong sense of connection and community. I'm not aware of any other factor in medicine--not diet, not smoking, not exercise, not genetics, not drugs, not surgery--that has a greater impact on our quality of life, incidence of illness and premature death.

In part, this is because people who are lonely are more likely to engage in self-destructive behaviors. Getting through the day becomes more important than living a long life when you have no one else to live for. As one patient told me, "I've got 20 friends in this pack of cigarettes. They're always there for me. You want to take away my 20 friends? What are you going to give me instead?" Other patients take refuge in food, alcohol or drugs: "When I feel lonely, I eat a lot of fat--it coats my nerves and numbs the pain." But loneliness is not just a barrier to fitness. Even when you eat right, exercise and avoid smoking, it increases your risk of early death.

Fortunately, love protects your heart in ways that we don't completely understand. In one study at Yale, men and women who felt the most loved and supported had substantially less blockage in their coronary arteries. Similarly, researchers from Case Western Reserve University studied almost 10,000 married men and found that those who answered "yes" to this simple question--"Does your wife show you her love?"--had significantly less angina (chest pain). And when researchers at Duke surveyed men and women with heart disease, those who were single and lacked confidants were three times as likely to have died after five years. In all three studies, the protective effects of love were independent of other risk factors.

Awareness is the first step in healing. When we understand the connection between how we live and how long we live, it's easier to make different choices. Instead of viewing the time we spend with friends and family as luxuries, we can see that these relationships are among the most powerful determinants of our well-being and survival. We are hard-wired to help each other. Science is documenting the healing values of love, intimacy, community, compassion, forgiveness, altruism and service--values that are part of almost all spiritual traditions as well as many secular ones. Seen in this context, being unselfish may be the most self-serving approach to life, for it helps free both the giver and recipient from suffering, disease and premature death. Rediscovering the wisdom of love and compassion may help us survive at a time when an increasingly balkanized world so badly needs it.