In March 2002, the Commonwealth Department of Family and Community Services announced the commencement of the Longitudinal Study of Australian Children (LSAC).1 This study is being implemented by a large multidisciplinary research consortium led by the Australian Institute of Family Studies. It will track the health and development of two national, population-representative cohorts of children recruited in their first and fourth years of life. The study will assess a broad range of individual, family and environmental determinants of health and wellbeing, and will focus on identifying factors that influence good and poor life-course outcomes. The study aims to provide data that will inform the development of health, family and social policy and services within Australia (Box 1). LSAC represents a significant government investment ($20.2 million over nine years) in longitudinal research on children, and it is timely to consider the extent to which it will address the shortcomings of past studies and add to our knowledge of children's health and development.

Longitudinal studies are essential to understand the causes of health problems and identify possible solutions.2 Using this type of study, Australian and New Zealand researchers have contributed significantly to our knowledge of health and development3-7 (Box 2). However, there are several reasons why Australia needs a new longitudinal study of children. Past studies typically recruited cohorts during the 1970s and 1980s8 and are therefore limited. First, the health profile of Australian children has changed significantly in recent decades. Emerging health concerns include increasing rates of atopic and chronic diseases and mental health problems, and unacceptably high levels of suicide, preventable injuries and harmful health behaviours during childhood and adolescence.9

Second, the environments in which children are being raised have altered profoundly in the last 30 years.9,10 There have been changes to children's immediate environments (family, childcare, schools and neighbourhoods) and the broader sociopolitical climate (including widening social disparities).10 Past study findings may not be relevant to modern childhood environments. In addition, past cohorts were typically drawn from confined geographical locations,8 and data on health and social services and policies may not be more widely applicable.

Third, there have been considerable advances over the last 30 years in theory, measurement tools and analytic techniques.11 Current epidemiological models highlight the central role of individual genetic and pathobiological factors in the expression of poor health and the need to examine multiple levels of influence (Box 3).12 Past studies have been unable to explore these factors adequately, often lacking sufficient sample sizes or the appropriate measures to disentangle multilevel influences.

LSAC addresses a number of these limitations. Specifically, it will:

• measure a wide range of outcomes and determinants;

• recruit cohorts nationally from rural–regional and urban settings; and

• have a sufficient sample size to explore multiple determinants and the occurrence of relatively rare events.1

However, it is unrealistic to expect this study to address all research needs. For example, LSAC will not capture sufficient children from minority groups to enable exploration of life-course pathways that may be unique to these populations. In addition, cost and methodological constraints are likely to result in the exclusion or under-representation of children from remote areas, and some forms of data collection will be too time-intensive or costly to use (eg, certain observational, biological or environmental measures). Also, LSAC will not involve the systematic provision of interventions. Given the growing evidence of the benefits to health that arise from prevention and early intervention,13 a strong case can be made for a coordinated program of longitudinal intervention trials to assess the impact of interventions delivered around key life-course transition times.14 Thus, studies of specific populations, studies addressing research questions that require costly data collection, and studies that involve the assessment of interventions could all add value. These could be designed in parallel with LSAC, or as studies nested within LSAC for creating efficiencies in research costs.

Australia is unique in geographical distribution of the population, family structures, ethnic diversity, social structures, policies and service provision. International research may have limited applicability in the Australian context. Nonetheless, it is important to consider Australian longitudinal research in an international context. Other Western nations are establishing new longitudinal studies,8 with European countries notable for coordinating studies that enable cross-country comparisons.15

LSAC may provide a foundation upon which other studies could be built to facilitate transnational comparisons and comparisons of changes to health pathways over time. Use of common design and measurement tools will facilitate these objectives. Longitudinal studies are expensive and demanding, not to be embarked upon lightly.2 Coordinated research efforts that strategically build upon the substantial national investment in LSAC may further enrich the evidence base for policy development and service provision to facilitate our nation's future health and wellbeing.

3: Ecological model of health across the life-course (modified from Lynch12)