How a Dog’s Size is Related to Lifespan

There are a number of factors that can determine a dog’s lifespan. We wish they could be with us much longer than they are. As a little boy once said, he felt that because they are already so good, G-d wants them with Him sooner.

Dogs can be lost to us through illness, disease, injury. One of the factors in a dog’s lifespan is size – small dogs live longer than large dogs. Large and giant dogs are considered seniors at between 6-7 years old, sometimes as early as 5 years old. But at those ages, small dogs are middle-aged.

In 2013, at the University of Gottingen, Germany, Dr. Cornelia Kraus researched and published papers on the connection between size and life expectancy in dogs. Dr. Kraus and her team of researchers discovered that size does make a difference. They found that each 4.4 lbs. of body weight decreased a dog’s lifespan by one month.

One of the reasons thought to be relevant to aging is that cancer is more frequently diagnosed in large dogs possibly due to faster cell growth. Also, we humans tend to treat small dogs differently. They are more pampered than their large cousins who may live riskier lives. We tend to be more rough and tumble with large breeds and they often have dangerous jobs.

In humans, the large concentration of the hormone, IGF-1 (insulin-like growth factor-1) can increase the risk of heart disease and cancer. Small dogs have lower concentrations of this growth hormone and are at lower risk of age-related diseases than large dogs.

The following are estimates of what age a dog is considered a senior according to its normal weight.

15 lbs. or less, about 9-11 years old

16-50 lbs., about 7-9 years old

51-80 lbs., about 6-8 years old

Over 80 lbs., about 4-6 years old

There have been many verified reports of healthy, small dogs reaching 18-20 years old. And of course, these estimates are just that. Each dog is an individual and this is only a guideline based on research.

You can judge the lifespan of your dog depending on its size, but with mixed breeds, it’s more difficult to determine how long they will live.

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