Sunday, June 08, 2008

Genetics and Life Expectancy

The major problem with using life expectancy to measure the quality of a country’s healthcare system is that life expectancy is affected by so many things other than healthcare: diet, crime, geography, education, and so on. And, of course, genetics. According to this article from New Scientist magazine (subscription required), the Japanese are more likely to have a key longevity-improving gene (which happens to reside in the mitochondrial, rather than nuclear, DNA) than other nationalities.
The most striking example comes from Japan. Here, there is a common variant in mitochondrial DNA, a change in a single DNA "letter". A decade ago Masashi Tanaka, now at the Tokyo Metropolitan Institute of Gerontology, and his colleagues reported that this tiny change almost halved the risk of being hospitalised for any age-related disease at all, while doubling the chance of living to 100. Most Japanese centenarians have the variant, but unfortunately for the rest of us it's very rare outside Japan.
Note that Japan always comes out at or near the top of life expectancy rankings.

Of course, we have long known (or at least suspected) that genetics had something to do with longevity. But for national health statistics, what matters is distribution; if the distribution of longevity-improving genes were independent of national origin, then genetic effects would wash out in international comparisons. As this example demonstrates, that’s not the case.


Anonymous said...

The smoking rate among adult Japanese men is almost 50%, while for women it is below 15%. I got that fact from a web search. I don't understand how their life expectancy can be so high considering the high level of smoking.

V said...

Anon - simple answer to your smoking question - it is because smoking isn't as bad for you as every state sponsored alarmist would have you believe.

Anonymous said...

Dear god,

Why didn't you make me Japanese?

Anonymous said...

The Japanese also embrace a diet high in fish and rice. The majority of Japanese have A+ bloodtypes and this hybrid vegetarian diet is highly beneficial to this particular bloodtype.

Anonymous said...

to the fist anon:

You are 50 times more likely to get lung cancer if you smoke 2 packs a day.

AnonEconomist said...

Another anon said:

"you are fifty times more likely to get lung cancer..."

So if they smoke and live long, then the number that is multiplied by 50 must be real small.

Anonymous said...

Jaspan's oldest guy is Tanabe Tamoji who is 113

Deborah said...

I was doing a search and this blog came up.

Japan's population was mostly non-smokers prior to WWII. Young men started smoking in masses during WWII. Women remained predominately non-smoking until the 1980s.

The age difference in life expectancy between men and women has been increasing as the men have aged to where most smokers die, in their 60s and 70s. Non-smokers tend to make it to 80s and 90s. The data you read on life expectancy is always 5-10 years out. So, in the next 10-15 years the almost 100% non-smoking aged male population influence on the male data will disappear.