Inequalities in the transition of cerebrovascular disease mortality in New South Wales, Australia 1969-1996

The development and experience of epidemiological transition theory over four decades: a systematic review

BACKGROUND

Epidemiological transition (ET) theory, first postulated in 1971, has developed alongside changes in population structures over time. However, understandings of mortality transitions and associated epidemiological changes remain poorly defined for public health practitioners. Here, we review the concept and development of ET theory, contextualising this in empirical evidence, which variously supports and contradicts the original theoretical propositions.

DESIGN

A Medline literature search covering publications over four decades, from 1971 to 2013, was conducted. Studies were included if they assessed human populations, were original articles, focused on mortality and health or demographic or ET and were in English. The reference lists of the selected articles were checked for additional sources.

RESULTS

We found that there were changes in emphasis in the research field over the four decades. There was an increasing tendency to study wide-ranging aspects of the determinants of mortality, including risk factors, lifestyle changes, socio-economics, and macro factors such as climate change. Research on ET has focused increasingly on low- and middle-income countries rather than industrialised countries, despite its origins in industrialised countries. Countries have experienced different levels of progress in ET in terms of time, pace, and underlying mechanisms. Elements of ET are described for many countries, but observed transitions have not always followed pathways described in the original theory.

CONCLUSIONS

The classic ET theory largely neglected the critical role of social determinants, being largely a theoretical generalisation of mortality experience in some countries. This review shows increasing interest in ET all over the world but only partial concordance between established theory and empirical evidence. Empirical evidence suggests that some unconsidered aspects of social determinants contributed to deviations from classic theoretical pathways. A better-constructed, revised ET theory, with a stronger basis in evidence, is needed.

Differential impacts of health care in Australia: trend analysis of socioeconomic inequalities in avoidable mortality

BACKGROUND

Recent avoidable mortality trends in Australia suggest that health care has made a substantial contribution to reducing mortality. This study investigates if the benefits of health care have been distributed equally by comparing declines in avoidable with non-avoidable mortality over time by socioeconomic status (SES).

METHODS

We calculated avoidable and non-avoidable mortality rates in Australia by small areas for 1986, 1991, 1997 and 2002. We performed pooled cross-sectional trend analysis of indirectly standardized mortality rates by SES and year, modelling using Poisson regression with over-dispersion. Socioeconomic inequalities were quantified using the relative (RII) and slope (SII) index of inequality.

RESULTS

The annual percentage decline in avoidable mortality at the higher end of the socioeconomic continuum (5.0%; 95% CI: 4.7-5.4%) was larger than at the lower end (3.5%; 3.2-3.8%), with increasing relative inequality between 1986 (RII = 1.54; 1.46-1.63) and 2002 (RII = 2.00; 1.95-2.06), greater than that in non-avoidable mortality (P = 0.036). In absolute terms, avoidable deaths fell annually by 7.4 (6.9-7.8) and 8.4 (7.9-8.9) deaths per 100 000 at the higher and lower end of the spectrum, respectively, with absolute inequality decreasing between 1986 (SII = 97.8; 87.6-107.9) and 2002 (SII = 81.5; 74.6-88.5).

CONCLUSIONS

Health care has contributed to decreasing the absolute SES mortality gap. However, advantaged people have obtained a disproportionate benefit of health care, contributing to widening relative health inequalities. A universal heath care system does not guarantee equality in health-care-related outcomes.

Socioeconomic status and stroke

This paper reviews the current evidence for the association between socioeconomic status and stroke incidence, survival, mortality, and other outcomes. The evidence is strongest for mortality and incidence of stroke, with high rates of stroke in low socioeconomic groups being a consistent finding. Low socioeconomic groups also have lower survival and greater stroke severity than high socioeconomic groups, although there is less evidence for this association. The mechanisms through which socioeconomic status affects stroke risk and outcomes are unclear but some studies report that differences in risk-factor prevalence could account for some of the variation. We discuss the implications of these findings and make recommendations for future research. Studies using prospective population-based methods with improved control for confounding factors are needed to confirm or refute these associations. Understanding the causal associations between socioeconomic status and stroke will allow interventions to be appropriately targeted and assessed.

A framework for modelling differences in regional mortality over time

STUDY OBJECTIVE

To present a conceptual framework for testing differences in mortality for small geographical areas over time using the generalised linear model with generalised estimating equations. This framework can be used to test whether the magnitude of regional inequalities in health status has changed over time.

DESIGN

A Poisson regression model for correlated data is used to investigate the relation of population health status to demographic, geographical, and temporal explanatory variables. Differences between regions at one or more points in time are tested with linear contrasts.

SETTING AND PARTICIPANTS

A case example shows the application of the framework. All cause mortality and cause specific mortality were compared for three rural regions of Manitoba, Canada between 1985 and 1999. The data were obtained from Vital Statistics records and the provincial health registry.

MAIN RESULTS

Tests of linear contrasts on the regression coefficients for time and region show an increase in the magnitude of the difference in the risk of all cause mortality and heart disease mortality between northern and southern regions of the province for the 1985-1989 and 1995-1999 time periods. No significant differences are identified for cancer, injury, or respiratory disease mortality.

CONCLUSIONS

The proposed framework enables testing of a variety of hypotheses about differences between regions and time periods and can be applied to other measures of population health status.