While many pet owners are sure their companions benefit their health, few take that belief as far as Mike Lingenfelter. The Alabama man credits Dakota, his Labrador retriever, with detecting several heart attacks before Lingenfelter knew he was having them.

Once, Lingenfelter said, Dakota -- trained to encourage its owner to be active -- could not wake him despite repeated nudges and pokes. The Lab woke Lingenfelter's wife, who discovered Lingenfelter having a heart attack. The dog's action got him to the hospital in time, Lingenfelter said.

To explore health claims made about human-animal relationships, two journals last month teamed to review 20 published studies on the topic. The papers included examinations of the effect of pet ownership on human health; on whether getting close to nature is good for your health (yes, said one study); if swimming with dolphins can help relieve depression (it can, said another); and if snakebites can kill (duh).BMJ (formerly British Medical Journal) and a veterinary journal conducted the review.

The pet owning study reviewed research conducted since the 1980s that has helped popularize what BMJ called the "view that pet ownership could have positive benefits on human health." Reputed benefits include higher survival rates from heart attack, lower use of doctors' services, a reduced risk of asthma and allergies in children exposed to pets during the first year of life, reduced risk of cardiovascular disease and better physical and psychological well-being in the elderly.

But other research has failed to confirm many of these findings, according to BMJ.

On the allergy question, in a study published in May in Current Allergy and Asthma Reports -- which was one of the studies reviewed for the BMJ report -- researchers found that dog ownership may offer protection against developing an allergy to the animal, but that the evidence fell short of proof. For cat owners, the allergy study's authors wrote, some findings showed an increase in risk for allergies and asthma, while others showed a decrease.

According to BMJ, the pet ownership study suggests that researchers should focus less on "whether pet ownership per se confers measurable physical benefits, but [instead on] the role that pets have in individual people's lives -- namely the contributions of the pet to quality of life or the costs to well-being through a pet's death." That, BMJ says, requires people to accept a broader definition of health that includes physical and mental well-being and a "sense of social integration."

Such improved well-being and social networking can result in healthy lifelong relationships, said Herbert Nieburg, a psychologist in private practice in Connecticut who is an expert on the effects of pets on human health. "If you speak to a lot of people who are married, many of them will tell you they met while dog-walking," he said. "It's sort of like a magnet in a sense, especially for people who may not be comfortable walking up to people."

Nieburg, the author of "Pet Loss: Thoughtful Guide for Adults and Children" (Harper, 1996), said that pets provide a "wide gamut of benefits."

"People with pets tend to describe themselves as happier, less depressed and feel as if they have this safe, unconditional friend who is there for them," said Nieburg. The death of a pet, he said, can sometimes represent a more profound loss to an owner than a relative's death. "In some cases, pets are involved in their life more than family. [The] dog or cat was in their life and gave them tremendous amounts of joy," he said.

According to the BMJ study, researchers have posited three theories to explain apparent links between pet ownership and improved human health. Such research is continuing, including a study Nieburg is planning to probe why pet ownership sometimes prevents those planning to commit suicide from killing themselves.

Here's a summary of the theories mentioned in the study:

* It's all an illusion. Factors other than pet ownership -- such as age, personality traits and economic or health status -- account for perceived gains in health. These factors "impact on the decision to own a pet and thus produce an apparent [but deceptive] link between pets and health," according to the study. You can almost hear the howls of pet owners.

* A pet helps you make friends. Pets may serve as icebreakers of sorts, enhancing their owners' social interaction with other people. This promotes a sense of well-being and "alleviates feelings of loneliness and social isolation," particularly in the elderly and those with physical disabilities, the study reports.

Some groups, convinced that contact with animals can benefit socially isolated individuals, arrange for volunteers to bring their pets into hospitals, nursing homes, correctional facilities, shelters and other facilities so that residents can interact with animals. "We've seen remarkable outcomes with individuals [including those] who thought they weren't lovable," said Dianne Bell, a program manager for the nationwide Pet Partners program run by the Delta Society, based in Bellevue, Wash. The Pet Partners experience, she said, gives isolated people the "opportunity to open up and share their issues, realize that it's safe, [that] it's okay to be able to express those feelings."

* A pet serves as a stress-buster. This theory suggests that the nature of the pet-human relationship may, in itself, positively impact health. This relationship may have a "powerful influence on well-being by providing emotional support" and may reduce the pet owner's perceptions of stressful events and provide confidence that there is a way to cope with stressful situations. "Social relationships, or lack thereof, seem to constitute a major risk factor for health, rivaling the effects of well-established risk factors such as cigarette smoking, blood pressure, blood lipid concentrations, obesity and lack of physical activity," according to the study.

As for Lingenfelter, who chronicled Dakota's heroics in a book titled "The Angel by My Side" (Hay House, 2002), he says he is living proof that a dog can save a life.

"Dakota made me get out of bed," he said. "It was a healing process that never ended."

To view the pet study, visit http://bmj.bmjjournals.com.

Comments: paynej@washpost.com.