By: Karl Pettersson

Re-posted from: https://static-dust.klpn.se/posts/2022-03-27-transition.html

Life expectancy and transition in cause of death patterns

This week, the Swedish statistical agency has published life tables for
Sweden 2021 (Statistics Sweden 2022). With the first waves of the COVID pandemic, life
expectancy at birth decreased from 84.73 years for females and 81.34
years for males in 2019 to 84.29/80.60 years in 2020. For 2021, the
numbers were again 84.82/81.21 years. This reflects, of course, the
decreased COVID mortality due to vaccination. Moreover, the flu A(H3N2)
wave, which peaked around Christmas with rather high rates of illness
among young people, did not cause substantial excess mortality, which
may, in part, be due to people with respiratory symptoms having less
contacts than usual with older people and other risk groups.

The increase in life expectancy in Sweden, and many other countries, up
until the mid-20th century was largely driven by decreasing childhood
mortality, which also caused changes in the cause of death patterns,
with directly communicable diseases becoming less common relative to
age-related diseases, such as circulatory diseases and cancer. In
contrast, the continued increase in rich countries after that, which was
temporarily interrupted by the pandemic, is largely due to decreased
mortality at older ages.

Vishnevsky (2017) discusses the development in life expectancy and causes
of death after 1960 in Russia, compared to high-income countries, in
particular Western European countries. In the EU-15 countries,
age-standardised mortality rates from circulatory, external and
respiratory causes have decreased greatly since 1970, while cancer
mortality has decreased modestly. The proportion of deaths from
circulatory causes has also decreased (from nearly 50 percent to about
30 percent), while the proportion of deaths from cancer has increased
(from about 20 percent to about 30 percent). No such changes have
occurred in Russia, where life expectancy has not improved much since
the 1960s (although it has improved relative to the dramatic increases
in mortality during the 1990s).

From this, one might conclude that the increased life expectancy in rich
countries largely has been about decreased circulatory mortality.
However, Vishnevsky points out that focusing on standardised rates for
all ages hides a significant increase in life expectancy for those dying
also of non-circulatory causes. In Sweden, for example, the life
expectancy for people dying of cancer or other neoplasms increased 8.2
years for females and 7.6 years for males during to period 1960–2010.
The corresponding increase for circulatory diseases (where life
expectancy was higher than for cancer already in 1960) is 8.0/6.8 years.
It is clear that this reflects a marked decrease in cancer mortality at
young ages, a point similar to what has been made earlier by researchers
like Riggs (1994).

One factor not discussed by Vishnevsky is the impact of changing
practices in reporting causes of death over a long time. For example,
the increase in life expectancy has been particularly strong for the
residual category, other diseases, in Sweden, with 20.0 years for
females and 17.8 years for males. This category includes dementia, which
was a rare underlying cause of death in 1960. Back then, most people
with dementia probably had circulatory or respiratory causes reported
instead, and the other category was dominated by other causes, with a
much lower life expectancy.

In light of this, it may be interesting to compare the correlation
between general life expectancy and proportion of deaths ascribed to
different causes in varying countries more in detail. I made a Julia
package, MortIntl, which can be
used to analyse such trends, based on cause-specific mortality data from
WHO (2022) and life tables from University of California, Berkeley and Max Planck Institute for Demographic Research (2022). It uses a configuration similar to
my earlier Mortchartgen,
which I have used to generate Mortality
Charts, but extracts data directly from
the data files using AWK instead of relying on a SQL database.

Fig. 1 and fig. 2 show female and male life expectancy at birth in
relation to proportion of deaths from circulatory causes (as defined for
Mortality Charts) for
the Nordic and Baltic countries, with Iceland excluded due to small
population.¹

The charts clearly show that improvements in life expectancy continued
for a long time among, for example, females in Finland and Sweden, after
circulatory causes became dominant, without any substantial change in
the proportion of deaths ascribed to these causes. That proportion
really started decreasing after the 1980s, when dementia became more
commonly reported (see Mortality
Charts).

The Baltic countries, especially Estonia, have in recent years attained
a female life expectancy close to the Nordic countries, but the
proportion of circulatory deaths there is higher than it has been in the
Nordic countries at any point in time. In contrast, Denmark, has had a
lower proportion of circulatory deaths than the other Nordic countries,
a pattern which has been more pronounced in recent decades. The
difference in circulatory deaths between Denmark and Estonia in recent
years, when both have had similar life expectancy among females, is
greater than the temporal variation, over nearly 70 years, in any of the
Nordic countries.

From this, it seems that clear that great caution is warranted in
drawing any epidemiological conclusions from trends for officially
reported circulatory mortality over all ages.

References