The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 6 No.
5 • November-December 2003
Centenarians in Japan
A new study reports that the number of years needed for the population of centenarians (in Japan) to double has been halved in 29 years, after adjusting for the birth cohort numbers. This extraordinary increase in very long-lived individuals is a good example of how the fall in mortality rates has included not just an increase in average lifespan, but also the numbers of people reaching very high lifespans. (Nevertheless, the authors report, the increase did not involve a strong reduction in the dispersion of individual lifespan around average values, and the survival curves do not appear much more rectangular than 20 years ago.) The authors suggest that it is the emergence of a very old sector of the population (95 years and older) that is allowing the lifespan to continue increasing. The researchers report that the ratio of centenarians per 10,000 births has increased from 3.5 for the 1873 cohort (1.4 for men, 5.6 for women) to 49.6 for the 1902 cohort (16.3 for men, 84.5 for women). In September 2002, it is reported that 23 supercentenarians (110 and older) were living in Japan (17 women and 6 men). The number of those aged 105 and older had reached 850 by the same date (127 men, 723 women).
The mortality rates calculated for women from the population of those aged 100–104 show a decrease from 43% in 1973 to 30% in 1999. For men 100–104, the mortality rate decreased from 48% in 1973 to 35% in 1999. The data also suggest a continuing decrease in female death rates at age 105 and over, but death rates for men 105 and over seem to increase. However, the number of people, especially men, 105 and over is small.
So, although we do not see (at least in Japan) a discernibly more rectangular curve of survival versus time, the oldest (100 and over) people are becoming greater in number at an astonishing rate. How much of this is due to genetic factors, nutritional state, medical treatments, etc., remains to be determined.
- Robine et al. The emergence of extremely old people: the case of Japan. Exp Gerontol 38:735-9 (2003).