The Demography of Centenarians in England and Wales - article ; n°1 ; vol.13, pg 139-156

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Population - Année 2001 - Volume 13 - Numéro 1 - Pages 139-156
Thatcher Roger.-The Demography of Centenarians in England and Wales Using a new database, the article investigates the causes of the current explosion in the numbers of centenarians. It then examines the latest official projections for the future and their implications for the highest ages which are likely to be attained.
18 pages
Source : Persée ; Ministère de la jeunesse, de l’éducation nationale et de la recherche, Direction de l’enseignement supérieur, Sous-direction des bibliothèques et de la documentation.

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R. Thatcher
The Demography of Centenarians in England and Wales
In: Population, 13e année, n°1, 2001 pp. 139-156.
Abstract
Thatcher Roger.-The Demography of Centenarians in England and Wales Using a new database, the article investigates the
causes of the current "explosion" in the numbers of centenarians. It then examines the latest official projections for the future and
their implications for the highest ages which are likely to be attained.
Citer ce document / Cite this document :
Thatcher R. The Demography of Centenarians in England and Wales. In: Population, 13e année, n°1, 2001 pp. 139-156.
http://www.persee.fr/web/revues/home/prescript/article/pop_0032-4663_2001_hos_13_1_7234The Demography of Centenarians
in England and Wales
Roger Thatcher*
During the 1940s and 1950s a new demographic trend made its
appearance: death rates at very high ages (80 and over) started to fall
throughout the developed world. However, this was not at all obvious at
the time. In individual countries, the initial changes were small in compar
ison with normal fluctuations and there were often doubts about the relia
bility of the data. Also, changes at these very high ages attracted less
attention than the important changes which were taking place at lower
ages.
As time went by, the new trend at the very high ages became firmly
established and started to produce some noticeable effects. These included
a spectacular percentage rate of increase in the numbers of centenarians.
Also, it became clear that record ages, which many experts had previously
regarded as the highest ages which it was possible for members of the
human species to reach (first 112 years, then 115 years), were being
broken.
In 1990 the Cambridge Group for the History of Population and
Social Structure invited three interested researchers to collaborate infor
mally in a project on the maximal length of life. They soon decided that a
proper investigation would call for the examination of reliable data from
as many countries as possible. Between them, and with funding from the
Danish Research Councils and the U.S. National Institute of Aging, they
assembled and computerised all the published official statistics on deaths
at ages 80 and over in 30 countries since 1960, or earlier in many cases.
However, only 13 countries (which included England and Wales) had data
which were sufficiently extensive and reliable for detailed analysis. This
database on old age mortality has been used to produce most of the figures
and tables in this article. The full database is currently held at the Max
Planck Institute for Demographic Research in Rostock, Germany, where it
* Formerly Registrar General and Director of the Office of Population Censuses and
Surveys.
Population: An English Selection, 13 (1), 2001, 139-156 140 R. Thatcher
is identified for reference as the Kannisto-Thatcher (K-T) database.
Copies can be obtained by institutions and serious research workers on ap
plication.
An important feature of the new database is the method which is
used to construct estimates of the past population numbers at very high
ages. In countries which do not have registers, it is common to
find that many of the very high ages recorded in censuses are erroneous
and less accurate than the ages which are recorded in death registrations.
However, it is not necessary to use the censuses. Once all the members of
a given birth cohort have died, the dates of birth and death which are
recorded in their death registrations give enough information to recons
truct the numbers who were alive at each date in the past, at least at ages
where international migration can be ignored. By this method, known as
the method of "extinct generations" or "extinct cohorts," improved est
imates of past population numbers can be made retrospectively. Extensions
of the method can also be used to produce provisional estimates for
cohorts which are not yet fully extinct. These methods have been applied
to all the countries in the database.
In the case of England and Wales annual series were produced from
1911 to 1996, though the later figures are still provisional. As the volume
of data is large, the method of presentation in this article is mainly graphic
al, but the numerical data for selected dates are given in Appendix I.
In England and Wales there are also other estimates of the numbers
of centenarians, based on the censuses and on samples of national insu
rance pensioners. These alternative estimates are discussed in Appendix II.
The "Explosion" of Centenarians
Figure 1 shows the estimated numbers of centenarians (aged 100 and
over) from 1911 to 1996. Females now outnumber the males by more than
eight to one.
From 1911 until the late 1940s the number of centenarians was tiny,
only one or two hundred. They were very rare and were more objects of
curiosity than anything else. Then, from about 1950, the numbers started
to rise and by 1996 had already reached nearly 6,000. The are
still fairly small but the rate of increase has been very large, about 7% per
annum, roughly doubling every 10 years. No other demographic group has
"explosion." increased at anything Although like these this figures rate, are which for has England been and fairly Wales described they are as tyan
pical. The same thing has been happening in all the other industrialised
countries for which there are reliable data.
There are several causes which have contributed to this "explosion":
increased numbers of births in the 19th century, improved survival from
birth to age 80, and then the new demographic trend in death rates at very I
Demography of Centenarians in England and Wales 141 The
Population Ined 363 00 6,000 I III
5,000
Total // — 4,000
- 3,000 // -
//Females
— 2,000
- 1,000
n
1911 1921 1931 1941 1951 1971
Year
Figure 1 .- Population aged 100 years and over on 1st January
England and Wales
high ages. We shall examine and quantify these in turn. For this purpose
we shall need to bring together data from several different sources: the Off
ice for National Statistics (ONS) statistics for births, the Government Ac
tuary's Department (GAD) unpublished cohort life tables for survival from
birth to age 80, and the K-T database for survival above age 80. It will be
convenient to compare the cohort born in 1850 (which produced the per
sons who were aged 100 on 1 January 1951) with the cohort born in 1895
(which produced the persons who were aged 100 on 1 January 1996).
Births
The effect of births is easy to quantify. Between 1850 and 1895 the
number of births increased by 55% for males and by 56% for females. A
century later, these extra births will have increased the numbers of those
aged 100 by factors of 1.55 for males and 1.56 for females.
Survival From Birth to Age 80
There was a very considerable increase in the proportion who survi
ved from birth to age 80. This finding is illustrated in Figure 2, which is 142 R. Thatcher
derived from unpublished GAD cohort life tables. The horizontal scale
shows both the year of birth for each cohort and the year when it reached
age 80. For example, the first points on the left show that 7% of the males
and 11% of the females born in 1841 survived to reach age 80 in 1921. By
the end of the period, the survival rate had greatly improved. Of course,
the reasons are well known: better hygiene and sanitation, and improved
food, housing, living standards and medical treatment.
Survival, per cent
Born 1841 1851 1861 1871 1881 1891 1901 1911 1921
Reach 80 1921 1931 1941 1951 1961 1971 1981 1991 2001
Figure 2.- Survival from birth to age 80
England and Wales, based on civilian deaths
A striking feature of Figure 2 is the widening of the gap between the
lines for males and females in the cohorts born between 1871 and 1901.
Some epidemiologists have suggested a possible reason. These cohorts i
nclude the men who served in the First World War, when many servicemen
took up smoking. The life tables do not include war deaths, but many se
rvicemen who survived the war would have died of lung cancer later,
before reaching age 80. This factor would have contributed to the wide
ning of the gap. Another factor would have been the reduction in women's
deaths associated with childbirth.
The combined effect of these changes between the two cohorts born
in 1850 and 1895 was to increase the survival rate from birth to age 80 The Demography of Centenarians in England and Wales 143
from 8.46% to 15.76% (by a factor of 1.8( for males, and from 13.38% to
30.78% (by a factor of 2.30) for females.
Death Rates at Age 80
Figure 3 shows the death rates at age 80 from 1911 until 1995, for
males and females. Until at least the 1940s, the death rates at age 80 were
very high and had been high for a long time. People thought that not much
could be done about deaths at such a high age and indeed there were many
diseases for which people over 80 could not be treated, or it was not wor
thwhile to treat them. Then from about the 1940s or 1950s the death rates
at age 80 started to fall at a speed which shows up quite noticeably in the
new database: about 1.3 per cent per annum for females and about half as
much for males. It should be noted that the decline in male mortality has
accelerated in the last 20 years.
0.18
Males
0.10
1911 1931 1941 1951 1961 1971 1981 1991
Year
Figure 3.- Death rates at age 80
England and Wales
It is not suggested that age 80 was a precise watershed. However, it
illustrates how the trend at very high ages changed, when death rates
which had previously been stable started to fall. 144 R. Thatcher
In Britain, one might naturally wonder whether a change which star
ted in the 1940s or 1950s might have something to do with the Second
World War or with the setting up of the National Health Service, but the
same change occurred in countries which were not in the war and did not
have a health service. This was, however, a time when more doctors star
ted to treat people over 80 and there were also new treatments available,
like sulphonamides and penicillin. Since then there have been many more
medical advances. Also, some people have adopted healthier lifestyles and
there have been new policies about caring for the old and keeping people
alive as long as possible.
Survival From Age 80 to Age 100
Above age 80, the rate of decline of the death rates gradually tails
away, but even small changes at individual years of age can compound to
gether to produce large effects. It is convenient to look first at ages 80-99.
The simplest way to see the combined effects of all the changes in death
rates at these ages is to examine the rates of survival from age 80 to age
100, which are shown in Figure 4. The fact that there has been a large im
provement in the survival rates is immediately obvious. Again, the impro
vement is larger for females.
, Survival, per 10,000
0 Born 1841
Reach 80 1921
Reach 1001941
Figure 4.- Survival from age 80 to age 100
England and Wales The Demography of Centenarians in England and Wales 145
The actual survival rates from 80 to 100 are small in absolute terms,
but it is the rate of increase which matters. Comparing the cohorts born in
1850 and 1895, the rate of survival from age 80 to age 100 has increased
from 0.102% to 0.423% (by a factor of 4.15) for males and from 0.288%
to 1.559% (by a factor of 5.41) for females.
Thus the falling death rates at ages 80-99 have had more effect on
the numbers of centenarians than all the changes below age 80 combined.
Changes Above Age 100
So far we have been concerned with the increase in the numbers of
those aged 100. A further contribution to the total number of centenarians
(aged 100 and over) comes from the numbers of those above age 100.
These numbers have also increased, primarily because there has been
some decline in the death rates even above age 100.
At these ages there is a complication, because centenarians above
age 100 come from earlier cohorts than those aged 100. It is hard to disen
tangle these effects exactly, but their combined result can be measured,
from changes in the ratio of the number of those aged 100 and over to the
number aged 100. Between 1 January 1951 and 1 January 1996, this ratio
increased from 1.85 to 2.32 (by a factor of 1 .26) for males and from 2.06
to 2.59 (by a factor of 1.16) for females.
Conclusion on Causes
All the numerical factors derived in this analysis are assembled in
Table 1 . They show the contributions which each of the causes has made t
owards the total increase in the number of centenarians, which was 12-fold for
males and 20-fold for females. Of course, for calculating the combined effect
of more than one cause, the factors are to be multiplied, not added.
Table 1 .- Causes of the increase in the numbers of centenarians between
1 January 1951 and 1 January 1996, England and Wales
Increases the total number of
centenarians by factors of Cause
Males Females
Increase in births between 1850 and 1895 1.55 1.56
Improved survival from birth to age 80 1.86 2.30 from age 80 to age 100 4.15 5.41
Changes above age 100 1.26 1.16
Net decrease due to war deaths, net migration and other causes 0.80 0.89
Product of the above factors: Increase in the total number
of centenarians 12.08 20.01
Source: See text. Derived from ONS vital statistics, GAD unpublished cohort life tables and the K-T database. 146 R. Thatcher
Table 1 also has a line showing the effect of war deaths and net mi
gration, which are not taken into account in the cohort life tables. These
factors would have reduced the total number of centenarians, as indicated
by the fact that the factors in Table 1 are less than 1. The cohort of males
born in 1895 was particularly affected by war deaths in 1914-1918. This
line has been quantified as a residual and the factors may possibly include
other causes, not separately identified.
The conclusion of Table 1 is that by far the largest single cause of the
"population explosion" has been the new trend of falling death rates and
increasing rates of survival between age 80 and age 100. This is also the
least well understood of all the causes. For further discussion and referen
ces on this point see Vaupel (1997).
Projections of Future Numbers
Projections of the future numbers of centenarians depend very hea
vily indeed on what assumptions are made about the future trend of death
rates at ages 80 and over. For the longer term, there are conflicting views.
Many people are confident that there are tremendous medical advances
still to come and that death rates at old ages will continue to fall, perhaps
even faster than ever. Others fear that economic pressures may make it dif
ficult to increase indefinitely the amount of money which is spent on the
old, paying for increasingly expensive treatments and care for continuin-
gly increasing numbers of old people. Also, in the longer term there are
potentially adverse developments, such as the emergence of new viral di
seases or the effects of global changes, which are not altogether
impossible.
However, whatever the uncertainties about the long-term future, we
are fortunate in starting from a position where there is a very clear and
well-established trend (see Figure 3). Vaino Kannisto, an international
authority on old age mortality, has recently given a very interesting ap
praisal of future prospects as he sees them (Kannisto 1997). His analysis is
based on the 13 industrialised countries in the new database and he is pr
imarily concerned with the average level which their death rates will even
tually reach, rather than with the exact timing of events. He first considers
what will happen if the death rates eventually reach a level which is as far
below their level in the 1980s as the 1980s rates were below their level in
the 1960s. He is not suggesting that the rates will fall steadily to this level
and then suddenly stop. Far from it. He deliberately takes no view on the
speed at which death rates will fall or on whether or when they will acce
lerate or decelerate. These things may vary from country to country. He
simply considers the properties of a stationary population with death rates
which have fallen to the level defined in this way. He calls this
"Scenario I" and he considers that death rates at this level are almost cer
tain to be reached. The Demography of Centenarians in England and Wales 147
Next, he considers a stationary population in which the death rates
are twice as far below their level in the 1980s as the 1980s rates were be
low their level in the 1960s. He calls this "Scenario II" and he regards this
level of death rates as realistic, though again he gives no view on when
they will be reached. Finally, he considers death rates at a level which is
three times as far below the 1980s rates as the 1980s rates were below the
1960s rates. He calls this "Scenario III" but finds that the resulting death
rates are so low that their plausibility may be questioned.
The official national population projections for England and Wales,
produced by the Government Actuary's Department (GAD), include pro
jections of the total numbers of centenarians from 1996 to 2036. GAD's
projections are continued to 2066, but only at the UK and GB level. Howe
ver, for the purposes of the present paper, GAD have provided comparab
le England and Wales data to 2066. Figure 5 shows these projections
against the background of Kannisto's Scenarios.
Thousands 160
140
120
Published"
official
projection
Unpublished
continuation Ч-- 20
Actual (1 Jan.)
1981 2001 2021 2041 2061 2081
Year
Figure 5.- Projected number of centenarians
England and Wales
In Figure 5, only the full line at the extreme left represents somet
hing which has actually happened. This is the increase up to 5,800 cente
narians in mid- 1996. The official published projection then shows an
increase to 39,000 centenarians in 2036, and the continuation shows a fur-