It's like this in all species, not only dogs, I think even Peat talked about it in some interviews. I think longevity statistics by country are not relevant as they can be skewed very easily by different criteria for counting infant mortality. You can get an idea of it by browsing the articles I shared below.Matt Stone is obsessed with the idea of small dogs having higher metabolism than big dogs therefore small dogs live longer but while true for dogs you can't adopt this logic on humans directly. I can't comment on the study yet but if you look at populations the Scandos & Canadians rank among the Top 15 in longevity. Also people from the South of the Mediterranean to the Equator are the smallest and have the shortest life expectancy, exceptions are Suisse, Spain and Italy, maybe higher elevations areas play a role in longevity.
List of countries by life expectancy - Wikipedia
en.m.wikipedia.org
Also, I lived in Scandinavia for a while and can assure you that Scandinavians are no beacons of health; they are pretty unhealthy in general.
Scandinavians suffer from long, dark winters and alcoholism but still they rank in the top of height and longevity.
The question is how do you measure 'health'. In absence of patient data, for example in history & archaeology you look at height & tooth health as proxies for health and good nutrition. The result is taller populations are better nourished, they have better health and are longer living. I think the length of your developmental phase (growth phase) to you height is an important ratio. If you reach your final height at 16 instead of 25 this might compromise your health even if your 6 foot tall.
Infant Mortality: A Deceptive Statistic | National Review
Virtually every national and international agency involved in statistical assessments of health status, health care, and economic development uses the infant-mortality rate — the number of infants …
www.nationalreview.com
Infant Mortality Isn't A True Measure Of A Successful Healthcare System
Infant mortality is a serious issue that must be better addressed, but it will not improve unless we focus on the underlying social and economic issues causing this significant problem.
www.forbes.com
Don't Trust Cuban Health Care Statistics | Mises Institute
We’ve long been told that Cuba’s health care system is one of the greatest in the world. In spite of the fact that health usually correlates with wealth in
mises.org
But whatever the problems with longevity statistics, your argument does not hold when you look at East Asians and how small and generally healthier than Westerners they are. It would simply be impossible for them to be like that if height was the main result of good health. Asians are even by far the longest living if we only look within the United States (like this we exclude the problem with infant mortality counting criteria), as Matt Stone writes in the Blue Zones article I shared in my post above. But I disagree with Matt about interpretation of these statistics (i.e. that they are innately genetically predisposed to be smaller and therefore healthier); I think Asians have less of an epigenetic burden than Westerners due to previous healthier habits, plus their diet and lifestyle retain certain healthy aspects even when they move to the US. I think if they adopted the Western diet and lifestyle completely, their height would slowly (over many generations) increase while their health would deteriorate to match that of Westerners.