Colin Mathers

The burden of disease and injury in Australia

An overview of the results of the Australian Burden of Disease (ABD) study is presented. The ABD study was the first to use methodology developed for the Global Burden of Disease study to measure the burden of disease and injury in a developed country. In 1996, mental disorders were the main causes of disability burden, responsible for nearly 30% of total years of life lost to disability (YLD), with depression accounting for 8% of the total YLD. Ischaemic heart disease and stroke were the main contributors to the disease burden disability-adjusted life years (DALYs), together causing nearly 18% of the total disease burden. Risk factors such as smoking, alcohol consumption, physical inactivity, hypertension, high blood cholesterol, obesity and inadequate fruit and vegetable consumption were responsible for much of the overall disease burden in Australia. The lessons learnt from the ABD study are discussed, together with methodological issues that require further attention.

Gains in health expectancy from the elimination of diseases among older people

PURPOSEnThis paper examines a health expectancy based approach to obtaining disease-specific measures of the contribution of health problems to loss of healthy life among older people. Health expectancies combine mortality and morbidity into a single population health measure. The objectives of this study are to evaluate the usefulness of potential gains in health expectancies as a measure of health impact of various chronic diseases and injury among older people and to examine whether elimination of specific diseases and injuries leads to a compression or expansion of morbidity. Results are presented for Australians aged 65 years and over in 1993.nnnRESULTSnThe results highlight the importance of the chronic non-fatal diseases such as osteoarthritis and eyesight and hearing problems as causes of disability and handicap in older people. Elimination of such diseases results in an increase in healthy years of life while total life expectancy remains unchanged, leading to an absolute compression of morbidity. At the other extreme, elimination of highly fatal diseases such as cancer can result not only in an increase in healthy years but an even larger increase in years with disability, resulting in a relative expansion of morbidity.

Trends in health expectancies in Australia 1981–1993

Health expectancy indices combine the mortality and morbidity experience of a population into a single composite indicator. This paper summarizes and evaluates methods for the calculation of health expectancies and presents trends in the expectation of life with disability and handicap in Australia from 1981 to 1993. Unlike other countries for which recent health expectancy time series are available, Australian results indicate that the expectation of years with disability has increased for both males and females. Possible explanations for this are examined.

The burden of disease and injury among older Australians

The Australian Institute of Health and Welfare recently published a substantial new study entitled The Burden of Disease and Injury in Australia [l, 21. This study uses methods developed for the Global Burden of Disease Study [3] to quantify the loss of health from a comprehensive set of 176 disease and injury causes and for 10 major risk factors, using the Disability-Adjusted Life Year (DALY). The Australian Burden of Disease Study was carried out in close collaboration with the Victorian Department of Human Services, which has conducted a parallel state-level analysis of the burden of disease for Victoria [4, 51.

International Trends in Health Expectancies: a Review

Abstract. Are we living longer but in worse health? Are the increases in life expectancy at older ages in developed countries occurring because we are keeping sick or disabled people alive longer or because we are saving people from death but leaving them in states of disability and handicap? This question was addressed in a symposium entitled International Trends in Health Expectancies. This review paper summarises the international evidence presented at that symposium on trends in health expectancies in developed countries. Health expectancies provide a powerful tool for monitoring the health of older populations, testing hypotheses about the evolution of health, and developing public policy. The available international evidence of time series of health expectancies for older people suggests that increases in disability prevalence began in the late 1960s and 1970s at the time when mortality rates at older ages began to decline significantly, but that these increases were confined to the less severe end of the disability spectrum. There is no evidence of expansion of morbidity based on more severe measures of disability prevalence. Recently emerging evidence from Europe and North America suggests that disability prevalence rates among older people may be starting to decline and we may actually be starting to see compression of morbidity in low mortality populations.

Appropriate yardsticks for measuring population health

In 1994-95, there was an outbreak of blindness among kangaroos in south-eastem Australia. During investigations into the causes of blindness an Orbivirus of the Wallal serogroup was isolated’ which was found to cause blindness in suckling mice after intra-cranial injection (Azuolas unpublished). The genus Orbivirus has at least seven serogroups, of which some have been known to affect humans; an example is ColoradoXck Fever, a dengue-like fever which occurs in North America.* The Wallal serogroup is unique to Australia and the putative vectors are biting midges rather than mosquitoes. The isolation of this virus in association with blind kangaroos naturally raised concerns for human health. While no illness linked to Wallal viruses has been reported previously, the possibility remains that this virus causes mild, asymptomatic or rare infections. A serum neutralisation test was developed at theVictorian Institute of Animal Science using antigen from this virus which could be used for human antibody testing. We conducted a study to determine if the virus can infect humans, using a high risk group of volunteers, namely park workers involved in the culling of blind kangaroos and the harvesting of tissue samples. We also tested subjects for exposure to other arboviruses. Nine park workers were tested. None was positive for ‘Wallaltype’ virus. Two subjects with a history of Ross River Virus (RRV) disease has IgG antibodies for RRV and another with no history of disease had antibodies to Sindbis virus. Another worker had a low titre of antibodies to a dengue-like flavivirus, probably acquired in the Northern Territory. While this study does not exclude the possibility that human infection occurs, it provides some preliminary evidence that handling carcasses or tissues from infected kangaroos is not a high risk setting for transmission. Caution is required, however, as the specificity and sensitivity of the test are unknown. Recently, an increasing number of newly identified viruses in animals have been found to occasionally infect humans. These include the equine morbillivirus, the bat lyssavirus and the porcine paramyxovirus.’ Public health professionals and researchers may be increasingly presented with the problem of assessing what sort of risk newly identified animal viruses present to human and communicating this risk. When the risk is low either because illness is rare or mild, ethical issues may arise in causing unwarranted anxiety through testing. The paradox is that in the absence of studies such as this, risk assessment becomes much more difficult.