Since age data is so plentiful, naturally people have already compiled world records sorted for every age 9 to 99. This can also come in handy when when creating an Age-Graded Calculator, or available as raw excel data here. However the best, original source of many such records can be found at the ARRS website, where world-best times are also tagged by the runner's country of origin. Although sorting runners by about 50 individual countries could lead to over-separating the data, it seemed natural enough to group countries by continent, of which there are only five: North and South America (grouped as one), Asia, Oceania, Europe, and Africa).
Without further ado, here are the best 5 km, 10 km, 16 km (10 mile), half marathon, and Marathon road race performances by single age record, color-coated by the continent said runner originated.
And here are the relevant countries that represent each continent (country codes here):
North and South America: CAN, MEX, USA, BRA, and COL
Europe: AND, AUT, BEL, BIH, BLR, CRO, CZE, DEN, ENG, ESP, FIN, FRA, GBR, GER, IRL, ITA, LAT, MAR, NED, NOR, POR, ROM, SCO, SUI, SVK, SWE, UKR, and WAL
Africa: ALG, ERI, ETH, KEN, NAM, RSA, and TAN
Oceania: AUS and NZL
Asia: CHN, ISR, JPN, KAZ, KOR, and RUS
The African road race dominance is very clear among the 16 to 40-year-old road runners, both in the men and women's categories. Yet African running prowess wanes almost immediately past age 40.
Kenyan and Ethiopian runners (who comprise the majority of African records) have constrained their competition to the absolute fastest ages.
There are almost no south american runners who hold age records (only two countries have any at all: Brazil and Columbia), which is why I grouped them with North americans.
We see that most of the best masters runners come from Europe, both for men and women, between 45 and 62 years of age. If looking for a potential sub 2:20 marathoner over the age of 40, search for them in europe. There is clear evidence the best septu- and oct- agenarian runners hail from North America. The North American dominance for the men aged over 64 is uncanny, and almost as powerful as Kenyan dominance of the younger african years. For example, the world record holders for most 70 and 80+ agers are Ed Whitlock and Betty-Jean McHugh, both Canadian citizens. At the other extreme, a suspicious number of preteen records are from the United States (likely that many countries do not encourage or keep records of runners at that age, hence I omitted these from the figure).
Meanwhile the best of asian runners tend to appear as young teenagers, and then again peppered throughout their 40s to 70s. At what age range an Japanese, Chinese, etc runner will set a new record is anybody's guess.
In case you were wondering, here is the dominance for track-based age records, again only showing even-numbered ages for 3000m, 5000m, and 10,000m races:
Why do these trends exists? We know that, anecdotally, Kenyans rarely compete seriously once their 'prime' career is over (less prize money, family obligations). Thereafter we find recreational amateur runners, who are found principally in Canada, US, and Europe. That said, money still exists for master runners (e.g. Waterfront gives out $500 for the first 40+ runner). The Boston Marathon gives out similar money. These are much smaller purses than the overall winners (on the order of 5-10%). Consistent with this line of reasoning, only three of 20 fastest all-time male and female masters finishers have been Kenyans. Were these money purses to grow, perhaps so too might the African dominance extend past the age of 40. With an ever-aging population in most countries (e.g. in Europe), we may expect attention to older runners will grow.
Within the 40+ category of runners, some trends are less obvious. For example, why do Canadians aged 70+ do so well relative to others? Is it our better health care, or a statistical fluke? Canada, with its long winters, is not obviously favorable for older competitors. Americans should have good senior citizen runners. So I just don't know.
And why do runners from Australia and NZ do their best running, relatively speaking, aged 50-70 on a track surface? No obvious answer here. Furthermore, Asian age category records appear not to have any obvious trend for any age. I have no clue what influences these countries. It appears teenage girls in Asia compete at as high a level as Kenyans. We also know Japanese runners love distance running, and have long life expectancy, hence show up in age-60 marathon records. At the same time it is surprising that Japanese/Asian runners do to dominate more the 70+ age records.
To summarize. this post is intended to show dominance per continent for 'typical' road race distances at varies with age. To me this pattern serves as a reminder that race plays a minor role in explaining running talent. Since age and genetics are closely linked, it would seem inconsistent to claim Asians, are 'born to run', but only until puberty, thereafter Kenyans are 'born to run', but only until middle age, thereafter Europeans are 'born to run', but only until retirement age, when suddenly Americans senior citizens are now 'born to run'. Obviously even in a sport so simple equipment is barely needed, many factors remain at play.
PS, here's the full range: