Dogs are like small children. They tend to explore their environments by putting whatever they can find in their mouths, as well as sniffing about your carpet, your furniture, and your lap. It's no surprise, then, that your canine friend can be harmed by toxic chemicals in your environment. New research confirms that dogs living in smoking homes are more likely to suffer from DNA damage and show signs of premature aging than those living in non-smoking homes.
In people, the potential health risks of smoking and inhaling second-hand smoke are well documented. But to understand how environmental tobacco affects our pets, Natalie Hutchinson, a veterinary researcher at the University of Glasgow, recruited 42 dogs and their owners, approximately half of whom lived in smoking homes and half in non-smoking homes. Each of the dog owners completed a survey about their smoking habits, frequency, and whether they smoked indoors or stepped outside. Then researchers collected blood, hair samples, and cheek swabs from the dogs during a health checkup. They also offered free-of-charge neutering, and collected spare tissues for genetic analysis.
A year later, Hutchinson followed up with 25 of the pet owners and conducted some more tests. She found that certain biological markers, such as the presence of nicotine in dogs' hair, were much higher in dogs exposed to smoke at home and were related to the amount of smoking going on. "The fact that we found significant increases in various biomarkers over just a year's worth of data is the most worrying part for me," she says. "Dogs can live up to 10 to 15 years with us, which means they could be exposed to even more harmful effects over time."
But dogs that came from smoking homes were already showing signs of DNA damage that could lead to shorter lives, Hutchinson says. Their telomeres, which cap and protect the ends of chromosomes, were much shorter compared to dogs from non-smoking homes. Telomeres not only protect DNA from oxidative stress, once they reach a critically short length, cells stop dividing and may even die, Hutchinson explains.
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When Hutchinson and her colleagues examined the testicles of male dogs post-neutering, they also discovered increased expression of what's known as the CDKN2A gene , a cycle regulation gene that helps keep cells from growing or dividing to rapidly and has been shown in previous studies to be altered in dogs with certain canine cancers.
Other studies have also indicated that dogs living with smokers were more likely to suffer from respiratory diseases, such as asthma and bronchitis, and faced a higher risk of developing lung cancer than dogs that live in smoke-free homes.
Unfortunately, smoking outside of the home only helps a little bit, Hutchinson says. Smoke residue often remains on skin, clothing, furniture, and fur long after the air has cleared. And pets are pretty good at hiding signs of illness. Perhaps smokers may be motivated to kick the addictive habit for their four-legged family members, she says. "At the very least, it should become part of a standard discussion in a veterinarian's office so that people become aware of how their habits may affect their dogs."
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