Use of Western Australian linked hospital morbidity and mortality data to explore theories of compression, expansion and dynamic equilibrium.

Three hypotheses have been advanced to predict changes in population health in countries experiencing low birth and death rates, and increasing expectation of life. Determining which of these best accounts for changing patterns of illness and death is an important step in understanding both the public health and economic impacts of health interventions in an ageing population. The aim of this study was to use the WA Data Linkage System to evaluate the compression, expansion and dynamic equilibrium theories in Western Australia. Changes in life expectancy, average age at first-time hospitalisation and time spent in chronic disabling or activity limiting states were used to evaluate the competing hypotheses. Life expectancy increased by 4.0 and 2.6 years over the 24-year study period in males and females, respectively. However, average time spent with a diagnosed chronic disabling condition increased by 9.2 and 9.4 years in males and females, respectively. These results suggest that an increase in the "medicalisation of more serious morbidity" may be in operation in Australia.