Released yesterday in New Zealand:
Decades of Disparity II: Socioeconomic mortality trends in New Zealand
1981–1999
Public Health Intelligence Occasional Bulletin Number 25
Date of publication: March 2005
http://www.moh.govt.nz/moh.nsf/0/1999a3f85f9da156cc256fe9000ad7fc?OpenDocume
nt

The authors are Tony Blakely, Jackie Fawcett and June Atkinson (Wellington
School of Medicine and Health Sciences, University of Otago), and Martin
Tobias and Jit Cheung (Public Health Intelligence, Ministry of Health)

Executive Summary

Decades of Disparity: Ethnic mortality trends in New Zealand 1980–1999,
described the widening mortality inequality between Maori and Pacific
peoples compared to non-Mäori non-Pacific people in New Zealand over the
1980s and 1990s. The current report, the second in the Decades of Disparity
series, describes disparities and trends in mortality by socioeconomic
position over this same period for the entire population (ie, all ethnic
groups combined). A future report will thoroughly examine mortality rates by
ethnic group and socioeconomic position simultaneously.

Socioeconomic inequalities in mortality have been increasing in developed
countries during recent decades – at least in relative terms. In this report
we have used New Zealand Census – Mortality Study data to estimate
inequalities and trends in adult mortality by income, education and
occupational class. We present results for each of the 1981–84, 1986–89,
1991–94 and 1996–99 periods, and focus on differences in mortality by a
three-level grouping of income (where approximately a third of the
population is in each income group).

We measured the disparities in mortality between income groups in both
absolute and relative terms. Absolute inequalities are differences in
mortality rates between low- and high-income people. Relative inequalities
are the ratio of these mortality rates for low- compared to high-income
people. Given that all-cause mortality rates in New Zealand are trending
down for all socio-economic groups, then if absolute inequalities remain
stable relative inequalities must increase. If absolute inequalities
increase over time, then relative inequalities must increase even more.

Overall, we found that:
•     absolute socioeconomic inequalities in mortality among males and
females aged 25–77 years were stable on average over the 1980s and
1990s,whereas relative inequalities increased
•     relative inequalities in mortality among males and females aged
25–77 years increased more using income as the measure of socioeconomic
position (approximately doubling) than using education
•     increasing socioeconomic inequalities in all-cause mortality over
time were most notable among 25–44-year-olds
•     educational inequalities in mortality tended to be greater than
income inequalities among 25–44-year-olds, while the opposite was found for
45–59 and 60–77-year-olds.

All-cause mortality
The rate ratios for 25–77-year-olds, comparing low- to high-income groups,
increased from 1.43 in 1981–84 to 1.72 in 1996–99 among males and from 1.27
to 1.50 among females.

Life expectancy
Estimated life expectancy at birth (weighted for varying ethnic composition)
increased during the 1980s and 1990s for all three income groups. Gaps in
life expectancy between low- and high-income groups widened from 3.4 to 5.0
years for males but remained stable (or even slightly narrowed) from 2.9 to
2.7 years for females.

All-cause mortality gradients by socioeconomic position and ethnicity
For the purposes of this report we checked whether the association of income
and education with mortality was broadly similar between ethnic groups. In
relative terms it was, but in absolute terms the income and education
differences were greater among Mäori.

Avoidable, amenable and non-avoidable mortality
Mortality avoidable by prevention and treatment, and the subset of mortality
amenable to health services interventions, declined dramatically over the
1980s and 1990s, with absolute inequalities remaining stable over time and
relative inequalities more than doubling. This suggests that health services
in the broadest sense may have made a substantial contribution to widening
relative inequalities in mortality over the 1980s and 1990s.

Cardiovascular disease
Relative inequalities by income among 25–77-year-old males increased
steadily from a rate ratio of 1.38 in 1981–84 to 1.69 in 1996–99, whereas
the rate ratio among females increased from 1.38 in 1981–84 to 1.54 in
1991–94, then fell to 1.40 in 1996–99. Absolute inequalities were roughly
stable over time among males, but decreased among females (mostly driven by
decreasing absolute inequalities among 60–77-year-old females).

Cancer
Relative inequalities by income among 25–77-year-olds increased from a rate
ratio of 1.28 to 1.53 among males, and from 1.09 to 1.41 among females.
Absolute inequalities increased in parallel. (Background cancer mortality
rates are not changing much over time.) Both lung and non-lung cancer
contributed to the increasing inequalities by income. Increasing cancer
inequalities by education were more muted than by income, but were still
apparent.
Unintentional injury
Trends varied by sex, age and type of injury. Inequalities by income at any
one point in time were most pronounced for 25–44-year-old road traffic crash
mortality (rate ratios ranging from 1.58 to 2.22). However, there were no
clear trends over time in inequalities in unintentional injury mortality.

Suicide
Inequalities by income varied by sex and age. They were greatest among 25–44
and 45–59-year-olds, with up to three-fold higher suicide rates among low-
compared to high-income people at points during the 1980s and 1990s. Both
absolute and relative inequalities in suicide increased markedly during the
1980s and 1990s among 25–44-year-olds. (Background suicide rates for young
adults were increasing during the 1980s to 1990s.)

Contribution of specific diseases to trends in inequality
Cardiovascular disease made the largest contribution to the total
socioeconomic inequality in mortality – although its share decreased over
time among females. The contribution of cancer increased over time and may
overtake the contribution of cardiovascular disease in the near future. This
prediction may be overturned if the obesity epidemic causes a reversal of
the falling rates of cardiovascular disease mortality among (particularly)
low socioeconomic groups.

Policy implications
There are two main policy implications of the findings in this report.
First, the results are consistent with the view that widening of the income
distribution during the 1980s and 1990s exacerbated socioeconomic
inequalities in health. Therefore it seems reasonable to predict that
economic and labour market policies aimed at narrowing the income
distribution will reduce socioeconomic inequalities in mortality. Second,
trends in socioeconomic inequalities in mortality have varied by cause of
death – and are likely to continue to do so. As the chronic disease most
amenable to primary prevention and treatment, cardiovascular disease
mortality among lower socioeconomic groups is a high priority if we are
aiming to reduce inequalities in the future. Cancer mortality looms as a
major driver of socioeconomic disparities in mortality in the coming
decades. Policies and programmes to reduce overall cancer (both
tobacco-related and non-tobacco-related) incidence and mortality need to be
designed and implemented in such a way as to prevent the further emergence
of socioeconomic inequalities in cancer mortality. Such policies and
programmes include primary prevention, screening and access to new treatment
modalities.


Melissa Raven, Lecturer
Coordinator, Drugs and Public Health
Department of Public Health, Flinders University
G5 Flats, Flinders Medical Centre
BEDFORD PARK  SA  5042    AUSTRALIA
Phone (08) 8204 5714  Fax (08) 8204 5693  International 61 8
 

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