Do dogs with longer noses live longer? Elucidated by British research

Recently CNN.co.jp reported the following:

犬は鼻が長いほど長生き？　英研究で明らかに

2024.03.09 Sat posted at 14:15 JST

 （ＣＮＮ） あなたの愛犬は鼻が長い雄の小型犬か、それとも顔のパーツの比率が平均的な雌の中型犬か。もし、そのどちらかなら、愛犬は長い間あなたに寄り添ってくれる可能性が高いことが、最近の研究で明らかになった。逆に愛犬が「鼻ぺちゃ」だったら、あまり楽観はできないかもしれない。

英国の５８万４０００匹以上の犬のデータを対象とした大規模な研究が行われ、その結果が先ごろ発表された。それによると、体の大きさや性別に加え、鼻の長さも犬の寿命に影響を与える可能性があるという。

「ブルドッグのような平たい顔の中型犬の雄は、ミニチュアダックスフントやイタリアングレーハウンドのような顔の長い小型犬の雌に比べ、短命の可能性が３倍高い」と語るのは、英国最大の犬の保護団体、ドッグズ・トラストのデータサイエンティストで、サイエンティフィック・リポーツ誌に掲載されたこの研究論文の主執筆者でもあるカーステン・マクミラン氏だ。

同論文の執筆者たちは、１５５の犬種とミックス犬のデータを分析した。その結果、典型的なラブラドールレトリバーやボーダーコリーの平均寿命が１３歳強だったのに対し、平たい顔の短頭種は、ほぼ例外なく、他の犬種に比べ寿命が短かった。この短頭種の例としては、マスチフ（９歳）、イングリッシュブルドッグ（９．３歳）、フレンチブルドッグ（９．８歳）などが挙げられる。

短頭種の中で例外的に長寿なのがラサ・アプソだ。平均寿命は１４歳で、柴犬（１４．６歳）、パピヨン（１４．５歳）、ミニチュアダックスフント（１４歳）、イタリアングレーハウンド（１４歳）らと並び、最も平均寿命が長い犬種の一つだ。

しかし、調査結果の大半は予想されたパターン内に収まった。雌は雄よりも長生きし、小型犬は大型犬よりも長寿だった。鼻の長い中・小型犬の平均寿命は１２年以上だったのに対し、平たい顔の犬は、体の大きさに関わらず、１２年を下回った。

デザイナードッグをめぐる議論

この研究のさらに驚くべき結果の一つは、純血種の犬はミックス犬よりも約８カ月長生きすることが分かったことだ。

この結果は、ミックス犬は一般に近親交配犬に比べ、丈夫で健康であるという一般的に抱かれているイメージと合致しない。しかし、現在の研究では全体像を示すことはできないとマクミラン氏は言う。

今回の研究で使用された犬のデータは獣医師、犬種登録所、犬の救済機関、ペット保険会社から集められた。

そして純血種と交配種に分類され、交配種に関しては、遺伝的に多様な雑種と、コッカプー、ラブラドゥードル、キャバションといった意図的に交配して作られた「デザイナーブリード」は区別されなかった。

デザイナーブリードは、ランダムに異なる犬種同士を組み合わせた「ミックス犬」や自然淘汰（とうた）の産物ではなく、純血種同士を人為的に交配させて生まれた「ミックス犬」を指す。

現在、ドッグズ・トラストは、この人気の高いデザイナーブリードが、その親である純血種に比べ寿命が長いのか、短いのかを見極めるための新たな研究に取り組んでいる。

しかし、ワシントン大学の犬の寿命に関する専門家で、獣医師でもあるシルバン・ウルファー博士は、「デザイナードッグは比較的新しい現象であるため、まだ若い犬が多い」とし、これらの犬が成長し、高齢化する過程を調査することにより、この交配種の健康や寿命に関する理解がさらに深まるだろうと指摘した。

マクミラン氏も、この研究結果は数百万ものデータポイントを含んでいるが、ペットとして飼われている犬の生活の全体像を必ずしも表しているわけではないと語る。例えば、ペット保険に加入していない犬もいれば、定期的に獣医に通っていない犬もいる。

また同研究では犬の死因も考慮されていない。犬は安楽死の処置が取られることも多い。

マクミラン氏は「この論文が政策立案者、政府、獣医師、飼い主、そして誰もが『これらの犬はなぜ亡くなっているのか』と考え始めるきっかけになることを祈っている」とし、さらに次のように続けた。

「その疑問に答えるのは非常に難しいだろうが、ほんの少しずつでも答えを見つけていけば、犬の健康の大幅な改善に一歩ずつ近づく」

Translation

(CNN) Was your dog a small male with a long nose, or a medium-sized female with average facial proportions? If you're one of those people, your dog would be likely to stay with you for a long time, according to a recent study. On the other hand, if your dog had a flat small nose, you might not be so optimistic.

The results of a large-scale study involving data from more than 584,000 dogs in the UK had recently been published. According to the study, in addition to body size and gender, the length of a dog's nose could also affect it's lifespan.

``A medium size male dog with a flat face, such as a bulldog, is three times more likely to have a short lifespan than a small female dog with a long face, such as a miniature dachshund or Italian greyhound.'' Said Kirsten McMillan, a data scientist at the Dogs Trust, the UK's largest dog rescue organization, and lead author of the study that was published in Scientific Reports.

The study's authors analyzed data from 155 breeds and mixes. They found that while the average lifespan of a typical Labrador Retriever or Border Collie was just over 13 years, flat-faced brachycephalic breeds almost universally lived shorter lives than other breeds. Examples of brachycephalic breeds include mastiffs (9 years old), English bulldogs (9.3 years old), and French bulldogs (9.8 years old).

The Lhasa Apso was an exceptionally long-lived brachycephalic breed. The average lifespan was 14 years, making it the dog breed with the longest average lifespan, along with the Shiba Inu (14.6 years), Papillon (14.5 years), Miniature Dachshund (14 years), and Italian Greyhound (14 years).

However, most of the findings fell within expected patterns. Females lived longer than males, and small dogs lived longer than large dogs. While the average lifespan of small and medium-sized dogs with long noses was more than 12 years, the average lifespan of dogs with flat faces was less than 12 years, regardless of body size.

Debate over designer dogs

One of the study's more surprising results was that purebred dogs lived about eight months longer than mixed breed dogs.

This result contradicted the commonly held impression that mixed-breed dogs were generally stronger and healthier than inbred dogs. But McMillan said the current research didn't provide a complete picture.

Data on the dogs used in the study was collected from veterinarians, dog breed registries, dog rescue organizations, and pet insurance companies.

They were classified as purebreds and hybrids, and in terms of hybrids, there was no distinction between genetically diverse hybrids and deliberately crossed "designer breeds" such as Cockapoo, Labradoodle, Cavachon.

Designer breeds referred to ``mixed dogs'' that were created by artificially breeding purebred dogs, rather than ``mixed dogs'' that randomly combined different breeds, or the product of natural selection.

Currently Dogs Trust was undertaking new research to determine whether such popular designer breed had a longer lifespan or a short than its purebred parents?

However, Dr. Sylvan Wolfer, a veterinarian and expert on canine longevity at the University of Washington noted that, ``Designer dogs are a relatively new phenomenon, so many of them are still young,'' and that as these dogs grow older, studying the aging process will further improve our understanding of the health and longevity of these hybrids.

McMillan said the study, which included millions of data points, didn't necessarily represent the complete picture of the life of a dog kept as a pet. For example, some dogs didn't have pet insurance or didn't visit the vet regularly.

The study also did not take into account the cause of death in the dogs. Dogs were often euthanized.

McMillan said, "I hope this paper will encourage policy makers, governments, veterinarians, dog owners and everyone to start asking themselves, 'Why are these dogs dying?'", and continued with the following words.

"It's going to be a very difficult question to answer, but every little bit we can find will bring us one step closer to significantly improving dog health."

              So, according to a research report on dogs, in general a medium size male dog with a flat face is three times more likely to have a short lifespan than a small female dog with a long face. One of the study's more surprising results is that purebred dogs live about eight months longer than mixed breed dogs. This result contradicts the commonly held belief that mixed-breed dogs are generally stronger and healthier than inbred dogs. It is an interesting finding on dogs.

Note:

Brachycephalic is a term invented by Andreas Retzius (1742 – 1821) to denote those skulls of which the width from side to side was little less than the length from front to back, their ratio being as 80 to 100, as in those of the Mongolian type. Thus, taking the length as 100, if the width exceeds 80, the skull is to be classed as brachycephalic. The prevailing form of the head of civilized races is brachycephalic. It is supposed that a brachycephalic race inhabited Europe before the Celts. Among those peoples whose heads show marked brachycephaly are the Indo-Chinese, the Savoyards, Croatians, Bavarians, Lapps, Burmese, Armenians and Peruvians. (1911 Encyclopedia Britannica, Volume 4)