Tuesday, January 16, 2007
People spend billions annually on their pets -- feeding, grooming, even clothing their animals. They play with them, sleep with them, approve surgery for them and mourn for them, much as they would for people.
But does owning a pet make people healthier? Popular assumptions notwithstanding, science is still out on that question.
A new study out of Finland suggests the answer may be no. Pet owners, the study finds, smoke cigarettes more but drink alcohol less than those without pets. They also have a higher body mass index (BMI), a ratio of weight relative to height. Pet owners spend slightly less time playing organized sports than non-owners but take part more often in such activities as hunting, fishing and boating. Pet owners are also less likely to report having good health than non-owners.
The findings point in a different direction from many previous studies, which have suggested that pet owners enjoy such health advantages as lower cholesterol, triglyceride and blood pressure than non-owners, even after accounting for such variables as exercise. Previous studies also have shown that owning pets may relieve feelings of loneliness and encourage pet owners to exercise more, spend more time outdoors and socialize more, according to the Centers for Disease Control and Prevention.
But this area of research is filled with inconsistencies, with one study's findings often contradicting another's.
And because many of the studies are of poor quality and not much funding goes to finding new answers, said James Serpell, director of the Center for the Interaction of Animals and Society at the University of Pennsylvania School of Veterinary Medicine, "much of this is speculation"-- meaning more research needs to be done to find definitive answers. What seems most promising, he said, is the idea that pets offer social support -- something that can affect how people deal with stress, which is known to impact health.
"At some level it seems obvious to me [that pets are] providing exactly the same types of support as" other social networks, including family and friends, Serpell said. Still, "while we like our friends and our family, they're likely a source of conflict, but most animals are not. Most animals give but don't take much."
Gold-standard evidence of pets' benefits to human physical and mental well-being may be scant, but examples of their use for health purposes are not. For decades, household animals have been used to assist patients with medical conditions such as blindness or seizures, as well as to relieve depression and social isolation. But when the National Institutes of Health last thoroughly explored the health benefits of pet ownership 20 years ago, its experts hedged.
"Persuasive evidence was presented to conclude that pets are likely to be medically beneficial to some people's health," they wrote in a consensus statement. "However, much is to be learned about many of these relationships before broad generalizations of medical benefit can be made." No comparable group of experts has since been convened to reexamine the question.
The health differences found between pet owners and non-owners in the Finnish study, published in December in the online medical journal PLoS ONE, were small and may not apply to Americans, the authors say. What's more, the study found a "difference only in the proportions of people reporting 'good perceived health' and not in the proportion reporting 'bad health,' " said lead study author Leena Koivusilta, a researcher at the University of Turku, in an e-mail interview.
"We wanted to report the slight differences" between the pet owners and non-owners who both reported good perceived health "but, at the same time, to make sure that no 'larger than life' interpretations could be made," Koivusilta said.
Her analysis was based on a survey of more than 21,000 Finnish people who responded to a questionnaire as part of a 15-year health and social support study. Eighty percent of those who had pets reported good perceived health, compared with 82 percent of those without pets. Twenty-eight percent of pet owners smoked regularly, compared with 23 percent of non-owners; 33 percent of pet owners smoked occasionally, compared with 32 percent of non-owners; and 39 percent didn't smoke, compared with 45 percent of non-owners.
But overall, pet owners in the study also were less educated than non-owners, suggesting that any health benefits observed might be due to socioeconomic status rather than pet ownership, the researchers said.
"The grand message of the study could be that pets provide us all with a vast potential for health promotion as has been shown previously," Koivusilta said. "Walking your dog makes you feel better, for your sake and for your hairy friend's sake, and perhaps also helps you to lose some weight."
Some research has suggested that pets offer social support that acts as a stress reliever, which affects health. One such study, published in 2001 in the journal Hypertension, found that pet owners had lower blood pressure readings when undergoing mental stress than people who did not own pets.
A 1995 American Journal of Cardiology study reported that dog ownership by men was associated with decreased risk of death within one year of a heart attack, compared with those who didn't own dogs. A 1999 Journal of the American Geriatric Society study found that men and women who owned a pet scored better on a scale that measures the ability to complete daily tasks -- such as bathing and dressing themselves, preparing food and walking several blocks -- than peers who didn't own a pet.
In 2005 BMJ (formerly the British Medical Journal) published a review examining studies that helped popularize the idea that pet ownership positively affects human health. The review found that while some studies reported pet-owning benefits such as better physical and psychological well-being in the elderly and reduced risk of cardiovascular disease, many later studies failed to confirm these findings.
Given this inconsistency, the BMJ review suggested that researchers focus less on whether owning a pet offers measurable health benefits and instead on how pets affect individual quality of life and how humans are affected by a pet's death.
Future research also should tackle more specific questions, gleaned from what's already known. "If pets are another form of social support, [then] we should start to ask more directed kinds of questions about the kinds of people who would be more likely to benefit from having a pet -- maybe the kinds of people who don't have a strong social support network," Serpell said.