New Study: Dogs Can Smell Epileptic Seizures
A dog’s sense of smell is a truly fascinating work of nature and biology. They have an uncanny ability to sniff out drugs, explosives, and even diseases like cancer because canines are built to optimize this specific sense in ways that we couldn’t even comprehend in the context of our own five senses.
Dogs possess anywhere from 10,000 to 100,000-times as acute a sense of smell as humans. "Let's suppose they're just 10,000 times better," says James Walker, former director of the Sensory Research Institute at Florida State University. "If you make the analogy to vision, what you and I can see at a third of a mile, a dog could see more than 3,000 miles away and still see as well.”
That’s almost an apples to oranges analogy, though, considering we’re talking about smell and not sight here. Dogs have such a superior sense of smell because they have up to 300 million olfactory receptors in their noses, compared to about six million in our own noses. That’s as many as 50 million more receptors dedicated just to the ability to take in smell, while the part of their brain that actually processes those smells is actually 40-times larger than our own. What this translates to is a greater capacity for deciphering the most minute details of a given scent. For example, to equate that back to the “3,000-mile” analogy, a dog-cognition researcher at Barnard College, Alexandra Horowitz, describes this heightened ability with the example of our own ability to smell something like sugar added to our morning cup of coffee. For us, maybe a teaspoon of sugar would create a recognizable smell in that cup of coffee. But to a dog, that same teaspoon of sugar could be detected in one million gallons of water. That’s the equivalent of two Olympic-sized swimming pools worth of water.
According to new research, of all the fascinating things we know and can try to wrap our minds around involving a dog’s ability to smell, new research has just uncovered a really unique perk made possible by their noses. And it’s potentially more valuable to some humans than dogs themselves.
For years, select service dogs have been trained to respond to and even sometimes sense epileptic seizures before a person has one. While it might sound like one of the more abstract types of service for a dog, there hasn’t been a sufficient body of scientific evidence to either prove these dogs are effective or how some are able to do this. The research recently published in Scientific Reports suggests that it’s actually an odor emitted by humans during epileptic seizures that canines are able to detect, likely allowing us to train them more effectively.
The study itself was pretty small but still revealing. Researchers took the sweat samples (that’s right) from the hands, forehead, and neck of seven patients with different types of epilepsy through different activities like resting, exercising, and even during actual seizures. The samples were then placed in cans and five dogs — Casey, Dodger, Lana, Zoey, and Roo — were then trained to recognize which can contain the sample of sweat taken during an epileptic seizure. Each dog completed nine tests involving samples from people they hadn’t encountered before. Lana and Roo were able to recognize the sample taken during a seizure two-thirds of the time while Casey, Dodger, and Zoey were able to recognize the correct sample with 100 percent accuracy.
"The results are extremely clear and constitute a first step towards identifying a seizure-specific odor,” the report reads. Although it’s important to note that the samples taken for this study were collected during a seizure and not before, therefore there was no control for a potential change in odor before or during a seizure, which would be more reliable in predicting one as opposed to recognizing it after a seizure has begun. Researchers also have yet to uncover how exactly an epileptic seizure even leads to a change in odor, to begin with. "It could lead to significant improvements in terms of seizure detection or prediction systems," the report adds.
The study and the research paper opens the door for the future of training dogs to aid and assist people who have epileptic seizures, as it’s the first time scientists have proven that humans emit a scent specific to having an epileptic episode. According to Amélie Catala, a doctoral student at France’s University of Rennes and the study’s lead author, there is hope that the findings might allow dogs to better respond or even sense seizures before they progress. Nor do researchers fully understand which molecules the dogs are detecting in this specific odor given off during a seizure.
“Studies like this are important, to provide a sound scientific foundation for the true capabilities of canines sensing seizures,” says Kenneth Furton, a chemistry professor at Florida International University not involved with the paper who has studied dogs and their olfactory detection abilities. According to Furton’s own research, dogs can sense seizures anywhere from 15 to 45 minutes before they happen, which, if trained properly, could allow them to alert people when they should take preventative medication or medication that can lessen the severity of a seizure. Furton even says appropriate and effective training for this could be executed in as little as a few weeks.
"Further research is needed but it is possible that the change in electrical activity triggers the releasing of some neurohormones that will, in the end, trigger the scent or that it is linked to stress-related molecules and pathways, or anything else - all hypothesis are still to be considered,” said Catala. "The study of odors by the use of dogs constitutes a fast, low-cost, non-invasive, and effective screening method of diseases that can be difficult to identify normally…Our next step is to try to see whether the scent is present before the seizure and if the dog can rely on it to alert someone,” she says.