Never mind the chewed slippers, the hair on the sofa, and the inexplicable barking at 3am. Having a dog in the home substantially reduces the risk of heart attacks and other fatal conditions, a major study has shown. Researchers found that dog ownership had a dramatic effect on people who live alone, cutting the risk of death from cardiovascular disease by 36%. In households with more people under the same roof, dogs had less of a positive impact, but still lowered deaths from heart disease by 15%, the work reveals. The findings emerge from a study of more than 3.4 million people in Sweden whose medical and pet ownership records were analysed to investigate the potential health benefits of dog ownership. Those who took part in the study were aged 40 to 80 years old and were followed for up to 12 years. Just over 13% had pet dogs. Tove Fall, professor of epidemiology at Uppsala University, and owner of a five-month-old Kooikerhondje puppy, said the health benefits of dog ownership appeared to be starkest for people who otherwise lived alone. We see effects in the single households that are much stronger than in multiple-person households, she said. If you have a dog you neutralise the effects of living alone. Last month, the leader of Britains GPs, Helen Stokes-Lampard, warned that loneliness was as bad for human health as a long-term illness. The estimated 1.1 million lonely Britons are 50% more likely to die prematurely than those with good social networks, making loneliness as harmful to the nations health as diabetes. While people who live alone are not necessarily lonely, many in the Swedish study seemed to benefit disproportionately from having a dog around. Working with her colleague, Mwenya Mubanga, on records from Swedens national registries, Fall also looked at deaths from any cause and found that people who lived alone with their dogs were a third less likely to die over the study period than those without dogs. For those in larger households, the risk of death was 11% lower among dog owners, the researchers write in Scientific Reports. The study cannot explain how dogs have a health-boosting impact, but the company alone may reduce stress and motivate people to live healthier lifestyles. In the study, Fall analysed the effects of different breeds and found that owners of dogs originally bred for hunting, such as terriers, retrievers, and scent hounds, had the lowest risk of cardiovascular disease. People who buy hunting dogs may be more physically active in the first place, because the dogs require so much exercise. The relationship may work both ways though, with livelier dogs effectively demanding that their owners do not slip into an overly-sedentary lifestyle. But Fall does not believe that getting more exercise explains all, or even most, of the health effects that come with dog ownership. My impression is that this has to do with social support, she said. Other explanations have been put forward, too. Having a dog around the house might influence what varieties of microbes take up residence on and in human bodies, and these may influence our health for the better, Fall said. In previous research, she showed that having a pet dog reduced a childs risk of asthma by 15%, lending support to the hygiene hypothesis which suggests that living in too clean an environment can increase susceptibility to allergies. Fall hopes to have more answers soon. One key question is whether dogs protect humans against heart disease by reducing blood pressure or through some other effect. It may be that dog owners like to be outdoors more, or are more organised, or more empathic, she said.
The Guardian, 17 November 2017 ; http://www.guardian.com