"There is nothing on earth to be more prized than true friendship." -- St. Thomas Aquinas.

For a man who spent most of his life tackling complex theological questions, St. Thomas Aquinas' sentiment about friendship is striking in its simplicity. St. Thomas spent years trying to reconcile Christian theology with ancient Greek philosophy. It just so happens that both the Bible and the Greeks place a high value on friendship.

According to Ecclesiastes: "Woe to the solitary man! For if he should fall, he has no one to lift him up." Aristotle notes, "The virtuous person is related to his friend in the same way he is related to himself, because a friend is another self."

As these sources suggest, our friends are good for more than just a good time. Friends take part in our spiritual existence, mirroring who we are and influencing how we live our lives. Recent research suggests that the effects of friendship are also good for our health.

For seniors, friendship can have a significant impact on longevity. In various studies, seniors with active friendships have been shown to outlive their friendless contemporaries by significant margins. Friends provide us with increased self-confidence and a sense of belonging. Scientists believe that these mental benefits, unique to friendship, may translate to better physical health.

One of the most extensive studies on the impact of friendship on senior health took place in Australia, tracking more than 1500 seniors over a period of 10 years. Researchers at Flinders University in South Australia found that those seniors with significant friendships in their lives were 22 percent more likely to live longer than those without close friends. Family ties appeared to have no effect on the survival rates of the participants -- seniors without family still lived longer if they had close friends in their lives.

Although the researchers involved in this study could not say for sure why having friends increased survival rates, they guessed that the reason had to do with reduced stress. When we have friends in our lives, we feel a deeper sense of connectedness with the world. Feelings of connectedness lead to reduced stress, and this may have a positive effect on the immune system.

Studies have also shown that having friends increases our confidence and outlook. In a 2008 study conducted at The University of Virginia, 34 students were taken to the foot of a steep hill. Some students were paired with their friends, while others confronted the hill alone. Each student was asked to estimate the steepness of the hill. The students who approached the hill with friends consistently estimated that the hill was less steep than those who approached it by themselves. For those who approached the hill with friends, the prospect of climbing the hill was less daunting.

The researchers concluded that the presence of friends expanded the students' confidence in what they could accomplish. Likewise, as we age, the increased confidence we get from our friends may play a role in helping us overcome illness and other life-shortening obstacles.

How many friends should you have?

Everyone has different social needs, and there is no standard "healthy" number of friends. We relate to people and appreciate our friends in different ways. Some of us are comfortable with a small number of very close friends; others prefer to maintain a larger sphere of connections. The Mayo Clinic suggests that you should pick the number and quality of friends that works best for you. The most important thing is to keep socially active and in touch with people outside of your immediate family. Whether you are a social butterfly, or more comfortable with a smaller circle of close confidantes, the friendships you nurture today are likely to lead to a longer life down the road.

Attending activities and participating in outings can be a great way to get to know people better. Residents at Youville and others who live in a community environment have the advantage of living among peers, sharing daily activities to help foster a more social lifestyle. No matter where you choose to live, here are a few tips for making friends and nurturing the friendships you already have:

-- Accept invitations -- when you are invited to an event, go to it!

-- Show an interest in others and maintain a friendly attitude.

-- Adopt a positive, healthy self-image. Try to avoid excessive complaining. Positive energy is a magnet for others who are interested in expanding their friendships.

-- Volunteering for a cause you care about is a great way to meet people in your community with similar interests.

-- Join a faith community. Being around people who share your personal beliefs and values is a great way to connect with potential friends.

All through life, friends play an essential role in our well-being. Whatever your age, maintaining an active social life may be one of the healthiest choices you can make for yourself.

Adam Johnson writes for Youville Assisted Living Residences, member of Covenant Health Systems, a Catholic, multi-institutional health and elder care organization serving New England. See www.youvilleassistedliving.org.