Each January, most of us make a list of New Year's resolutions — maybe we want to strengthen our bodies, or our resolve to eat better, or the determination to quit smoking. As it turns out, strengthening your social relationships may be an effort worth adding to your list of New Year's resolutions — for the good of your health.

Social connections like these not only give us pleasure, they also influence our long-term health in ways every bit as powerful as adequate sleep, a good diet, and not smoking. Dozens of studies have shown that people who have satisfying relationships with family, friends, and their community are happier, have fewer health problems, and live longer.

Conversely, a relative lack of social ties is associated with depression and later-life cognitive decline, as well as with increased mortality. One study, which examined data from more than 309,000 people, found that lack of strong relationships increased the risk of premature death from all causes by 50% — an effect on mortality risk roughly comparable to smoking up to 15 cigarettes a day, and greater than obesity and physical inactivity.

What makes social connections healthful

Scientists are investigating the biological and behavioral factors that account for the health benefits of connecting with others. For example, they've found that it helps relieve harmful levels of stress, which can adversely affect coronary arteries, gut function, insulin regulation, and the immune system. Another line of research suggests that caring behaviors trigger the release of stress-reducing hormones.

Research has also identified a range of activities that qualify as social support, from offers of help or advice to expressions of affection. In addition, evidence suggests that the life-enhancing effects of social support extend to giver as well as to receiver.

All of this is encouraging news because caring involvement with others may be one of the easiest health strategies to access. It's inexpensive, it requires no special equipment or regimen, and we can engage in it in many ways.

What counts

The quality of our relationships matters. For example, one study found that midlife women who were in highly satisfying marriages and marital-type relationships had a lower risk for cardiovascular disease compared with those in less satisfying marriages. Other studies have linked disappointing or negative interactions with family and friends with poorer health. One intriguing line of research has found signs of reduced immunity in couples during especially hostile marital spats.

Having a network of important relationships can also make a difference. A large Swedish study of people ages 75 and over concluded that dementia risk was lowest in those with a variety of satisfying contacts with friends and relatives.

Strengthening ties

For many of us, the recent holidays meant family gatherings, getting together with friends, and participating in special religious, community, and workplace activities. Such occasions are an opportunity to check in with each other, exchange ideas, and perhaps lend a supportive ear or shoulder. Now is a good time to strengthen your ties throughout the years to come.  Here are some ways to start:

• Focus on your most meaningful relationships.
• Choose activities to do together that are most likely to bring joy to you and the people you care about.
• Delegate or discard tasks that eat into your time, or do them together with family or friends.