Recently, studies have appeared in the medical literature suggesting that owning a dog could have a significantly positive effect on your health.
In these papers, the researchers combined the results of several smaller studies to provide greater statistical validity for their conclusions. In one paper, the authors calculated the risk of death in almost four million people followed up for around ten years. Dog owners were 24 per cent less likely to die during that period than those who did not have one.
The survival benefit was even greater in those people who had a history of a previous heart attack. The dog owners in this group had a 65 per cent reduction in risk of death compared to non-owners with previous heart attacks.
It might be assumed that the benefit of having a dog was caused by the exercise people get from taking them for a walk. However, people might be sceptical that this could confer such health benefits. Surely a stroll with a pet is not nearly energetic enough? Surely, there must be other influences at work?
Furthermore, associations between events do not prove that one event is the cause of the other and there may be many other explanations for the improved survival.
For example, there is strong evidence that people who have strong social networks are less likely to die prematurely. The companionship and affection between dog and owner might make a positive contribution to wellbeing.
A real effect on survival
However, a second paper, using data from Sweden, was able to take some account of issues like social and family networks and it, too, showed dog ownership to be associated with reduced risk of death after a heart attack or stroke.
Dog ownership meant that those who lived alone and who had a heart attack were 33 per cent less likely to die than heart attack patients who did not own dogs. Dog owners were also 27 per cent less likely to die following a stroke. Reduced risks were also seen in dog owners who lived with their families. Dog ownership seems to have a real effect on survival.
It seems that dog walking has greater health benefits than expected. But, can it really be true that exercise as mild as walking a dog prolongs your life? Current guidance in the UK suggests that, in order to get health benefits, adults should aim for at least 75 minutes of vigorous activity a week or 150 minutes of moderate activity.
However, a third paper published a few weeks ago suggested that the risk of early death could be reduced with lower levels of exercise.
A group of researchers from several different countries pooled the results of 14 studies which looked at the impact of running on mortality in around 230,000 people followed up for between five and 35 years. They found that those who went running had a 27 per cent lower risk of death during follow-up. Deaths from heart attacks were reduced by 30 per cent and deaths from cancer were 23 per cent lower in those doing some running.
The important conclusion the authors came to was that more was not necessarily better. There was no statistical link between the frequency, duration or pace of running and the survival benefit. Any running, even once a week, they concluded, was better than no running and higher doses did not necessarily produce greater reductions in mortality. These studies seem to show that the benefits of being active start at low levels of activity. Any exercise is better than none. Even a daily walk with the dog seems likely to prolong life.
Professor Sir Harry Burns is director of global public health at Strathclyde University