Can Dogs Detect Health Problems in People?

posted: 05/15/12
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Can dogs detect health problems in people?
LWA/Dann Tardif/Blend Images/Corbis | Darwin Wiggett/First Light/Corbis | Markus Altmann/Corbis

Imagine that instead of giving a urine sample or getting blood drawn when you need a diagnostic health test, you consult with a dog instead. It's a funny concept, but your pooch may have more in common with your doctor than you previously thought. We've long known that dogs have stronger senses than we do, with their sense of smell getting the most attention. That sense of smell is about 1 million times greater than ours, which is why they've been used in tracking and hunting since they became our companion animals. Today, dogs help us find everything from bombs to drugs, and it's simply amazing what they can do. In addition to smell, many dogs also have a strong "sixth sense"; they just notice things that we don't.

Doubtless, none of this comes as a surprise to you, especially if you have a dog. But did you know that your dog's keen senses could actually save your life? Sure, canines are known to alert people about fires or protect them from intruders, but in this case, we're talking about an internal "intruder," like cancer. If you think this sounds crazy, you're not alone; cancer specialist Dr. Leonard Lichtenfeld, who wrote about the phenomenon for the American Cancer Society's blog in 2010, admitted to laughing when he first read about a study in which dogs supposedly sniffed out cancer.

Lichtenfeld stopped laughing when more studies appeared, and you should take it seriously, too. Read on to find out why cancer-sniffing dogs are no laughing matter and learn about the other ways that dogs can detect human health problems.

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Cancer-sniffing Dogs
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While some aspects of dog senses are still a mystery to us, we do know that when it comes to smell, they're probably picking up on volatile organic compounds (VOCs) in the air. These microscopic chemicals exist in both gaseous and liquid states, and they're emitted by both biological and man-made substances. We can smell them, too; in recent years, things like paint have been criticized for the potentially toxic VOCs that they emit. Due to their superior sense of smell, dogs can detect VOCs in extremely tiny amounts. Exactly how well they can sniff out something depends not only on the breed but also on the individual dog -- some dogs are just better at it than others.

Going on this knowledge, several researchers in the past decade have successfully trained dogs to sniff out cancer. The first study read by Dr. Lichtenfeld took place in 2004 in England and was published in the British Journal of Medicine. Six dogs were trained to detect urine samples that belonged to patients known to have bladder cancer. While their 41 percent success rate wasn't amazing, it was higher than the 14 percent "coincidence rate" determined by the researchers. Since then, dogs have been trained to discern other forms of cancer, including skin, prostate, lung, breast and colorectal cancers, with increasing rates of success.

Two years after the bladder cancer study, researchers at the Pine Street Foundation in California trained dogs to sniff out both breast and lung cancer. Rather than sniffing urine samples, however, the dogs smelled breath samples from the patients. The results were startling -- they had an 88 percent success rate with breast cancer and a 97 percent accuracy rate with lung cancer. The most impressive study took place early in 2011, in which dogs in Japan detected colorectal cancer with 98 percent accuracy by sniffing breath samples. This is more accurate that the traditional diagnostic tests for the disease.

So far, the cancer-sniffing dog phenomenon has only been used in research, but scientists are hoping to identify and isolate the exact compounds dogs are detecting to create electronic cancer-sniffing devices. Up next, more health problems that dogs are helping people with right now.

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Dog Detectives
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While dogs probably aren't going to be used to diagnose cancer any time soon, they are at work right now helping people manage other diseases and health problems. You've probably seen service dogs assisting people who are visually, hearing or physically impaired, but dogs have been trained to do much more than help out people living with challenges like these. Service dogs are used today to assist people who have everything from neurological disorders to diabetes. Obviously, this is very different from directing a visually impaired person on the sidewalk or letting a hearing impaired person know that someone is at the door. This is where dogs' keen perception comes in. Instead of being trained to pay attention to outside cues, dogs can learn to pick up on signs from their owners that something is wrong.

In the case of people with psychiatric conditions like post-traumatic stress disorder (PTSD) or anxiety disorders, dogs can learn to tell when their human companion is feeling anxious or paranoid through body language and changes in behaviour. Dogs provide stability and emotional support; they also remind their handlers when to take medication. Service dogs for autistic people not only help them deal with processing auditory and visual stimuli, but they also alert them to behaviors they might not realize they're engaging in, such as self-harm or self-stimulation.

Dogs have also saved lives by alerting people to health problems before they even occur. Alert dogs let their type 1 diabetic human companions know that their blood sugar levels are off before the person feels any symptoms or takes a blood test. Low blood sugar changes the volatile organic compounds emitted through the pores of a diabetic; the dogs let their owners know of this change by whining or licking their hands. Dogs have also alerted humans to changes in their blood pressure or even let them know when a heart attack was imminent.

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