It is fairly common for media outlets to make a big splash when there is a case involving a severe dog attack in their area. This usually results in local politicians being pressured to find a solution to the "dog bite problem" and to find it quickly. On average, the risk of receiving a dog bite which is severe enough to require medical is about 3 to 4 per thousand people in the population each year. Epidemiologists tell us that that globally that would place dog bites among the top 12 causes of nonfatal injuries. These injuries are particularly distressing because in more than half of the cases young children are the victims.

There are a number of studies which show that the likelihood that a dog will attack someone varies depending upon the dog's breed. The data shows that certain breeds are much more likely to be reported as being guilty of inflicting serious and even fatal dog bites. For that reason many politicians have decided that the most expedient way to solve the problem of frequent dog bites is to simply ban, or strictly control, those breeds of dogs which have been shown to be the most common offenders. While, at first glance, this appears to be a simple and effective solution, it has excited controversy among dog owners who feel that such legislation often victimizes dogs who are well behaved and have committed no offense other than having been born as a member of a particular breed. Thus attempts to impose or to continue breed-specific bans often become the focus of heated public debates. For example, arguments over the "Dangerous Dogs Act" passed in the UK in 1991 continue to be the focus of a political maelstrom.

Source: Jan Jablunka photo — Creative Content License CC0

The exact nature of breed-specific legislation designed to ban or restrict certain types of dogs varies from one venue to another. However, looking over the sets of data available from Europe, Australia, and North America, it appears that such legislation most often does not have the desired impact. Often the reduction in dog bite frequencies is quite small or nonexistent. One scientific argument that could explain what appear to be such weak effects comes from the fact that the most common format of breed-specific laws focuses on controlling dogs when they are in public areas. Regulations usually require muzzling and keeping the targeted dogs on leash at all times. While that might reduce the number of dog bites out in the community, it is unlikely that dog owners would keep their on leash or muzzled within their home or other private spaces. If the specified dog breeds are inherently dangerous, then their bite frequency (presumably involving family members) in private living areas would not go down and this would water down or weaken the likelihood of seeing any reduction in bite frequency using pooled data that simply counts total dog bites regardless of where they occurred.

A new study, headed by Finn Nilson of the Department of Environmental and Life Sciences at Karlstad University in Sweden, provides some interesting and valuable data on the effectiveness of breed-specific legislation which gets around this and other methodological problems in previous studies. The data for this study was collected from Odense University Hospital in Odense, Denmark. Odense is the third-largest city in Denmark, with 188,000 inhabitants, and has one hospital with an emergency department. Specifically included in this study were all dog bite cases which showed up in the emergency ward over a 13-year period (between January 1, 2002 and June 31, 2015). This timing is important because in the middle of this time span (in 2010) Denmark passed a law banning the breeding, import, and new ownership of 13 dog breeds which the legislators identified as dangerous. In comparison to some other breed-specific regulations, the Danish law had some particularly draconian provisions. The most severe clause involved an immediate death sentence imposed upon all Pit Bull Terriers and Tosa Inus in the country. The remaining 11 breeds (American Staffordshire Terrier, Fila Brasiliero, Dogo Argentino, American Bulldog, Boerboel, Kangal, Central Asian Ovtcharka, Caucasian Ovtcharka, Tornjak and Sarplaninac), were spared from euthanasia; however, strict restraints were placed upon them. These dogs were forced to wear a muzzle and be on a leash in public places at all times. Taking so many presumably "dangerous" dog breeds out of circulation at the same time should be expected to have had an immediate effect on public safety.

To evaluate the effectiveness of the law, these investigators first separated the dog bite incidents into those which occurred in private spaces (like an owner's home) versus those that occurred in public areas. They then used some rather sophisticated time trend statistics to see if the ban had any effect on dog bites that were severe enough to require emergency ward medical attention. As I indicated earlier, there was no expectation for the breed-specific legislation to have any effect on dog bite frequencies occurring in private and home settings (where it is doubtful that any additional restraint or control was actually put on the targeted dogs), and the statistical analyses showed that to be the case.

Of course, the aim of the legislators was to reduce the frequency of severe dog bites in more public areas. Over the time period studied, there were 874 dog bites which occurred in public spaces and required emergency medical treatment. When the investigators mathematically fitted the trend line spanning the years before and after the law was introduced, their results can only be seen as quite disappointing for advocates of breed-specific legislation. You can see their results in the figure below: The red vertical line shows when the breed-specific legislation was introduced and the green horizontal line represents a zero change. Increased dog bite frequency is represented by points above the line, while the expected decrease in dog bite frequency would be represented by points below the line. Looking at this graph, you can see that there clearly was no abrupt drop in the frequency of dog bites following the legislation, and even when the results are tracked over the following five years, there is still no significant change.

Source: Data from Nilson et. al. (2018): SC Psychological Enterprises Ltd.

The researchers summarize their findings as follows:

"According to the results in this study, no effect of the legislation can be seen on the total number of dog bites, therefore supporting previous studies in other countries that have also shown a lack of evidence for breed-specific legislation. Importantly, compared to other studies, this study can show a lack of evidence using more robust methods, therefore further highlighting that future legislation in this area should be prioritized on non-breed-specific legislation in order to reduce the number and risk of dog bites."

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.