Introduction: Over the past few decades the
increase in life expectancy of the Japanese has
been a subject of keen interest among social and
medical scientists. Life expectancies for Japanese
men and women have more than doubled over
the past century. In the year 1995, the last year
for which national and prefectural life table data
are available, the Japanese had the highest life
expectancy in the world at 76.7 years for men
and 83.2 years for women. The rate of life
expectancy increase is slowing but it continues to
exceed that of most other countries. Within
Japan, life-table estimates by prefecture indicate
that overall life expectancy in Okinawa prefecture
has been higher (77.5 years for men and 85.1
years for women in 1995) than that of other
prefectures in all years that data has been
available. Moreover, despite outmigration of the
eldest birth cohort, and a relatively high
birthrate in the Okinawan population, very low
mortality at older ages has resulted in what may
be the highest centenarian prevalence in the
world for a country or state, at 33.6 per 100,000,
versus approximately 10 per hundred thousand
in most industrialized countries. However, as in
most industrialized countries, life expectancy
gains in Okinawa prefecture have been slowing
and the differences between prefectures narrowing.
This presentation will explore the Okinawan
longevity phenomenon within the context of the
dramatic increase in Japanese life expectancy as
a whole.

Methods: The contributions of different age
groups and causes of death to mortality
declines in post-war Japan are analyzed and
reviewed using standard demographic
approaches (i.e. decomposition procedures)
based on vital statistics and life-tables from the
Japan Ministry of Health, Labor and Welfare.
 

Results: Spectacular increases in Japanese life
expectancy during the 1950's resulted mainly
from reductions in deaths due to infectious
diseases. Reductions in two infectious diseases
(tuberculosis and gastroenteritis) accounted for
43% and 34% of life expectancy gains for men
and women respectively. These gains were
concentrated mainly in younger age groups.
Subsequent gains in life expectancy have been
concentrated mainly in older age groups, with
cerebrovascular mortality the most important,
accounting for between 25% to 43% of the
yearly gains for women and 28% to 51% of the
gains for men, from the 1970's to the 1990's. In
fact, a large part of the difference between
Okinawa and mainland Japan can be accounted
for by lower cerebrovascular mortality alone,
which latest available data (1995)reveal mortality
at 51.7% and 42.5% of mainland Japan levels
for men and women, respectively. Lower mortality
from the other two major chronic diseases of
aging, cancer and heart disease, accounts for
most of the remaining difference.
Conclusions: Okinawan longevity can be attributed
in large part to the low rates of chronic
diseases of aging, in particular, cardiovascular
diseases (coronary heart disease and stroke) and
cancer. The low rates of cerebrovascular disease
versus mainland Japan are particularly noteworthy.
However, life expectancy differences have
been narrowing in comparison with other
Japanese prefectures and it remains to be seen
how long Okinawa will retain its leadership
position.The authors acknowledge the support of the Japan Foundation for Aging and Health,
the Warren-Williams-Richardson Fellowship of
Harvard Medical School and the Japan
Ministry of Education, Science, Technology and
Culture (Monbusho). BJW is a Men's Associate
Research Fellow of the Hebrew Rehabilitation
Center for Aged, Harvard Medical School.