Letter to the Editor regarding ‘Optimising brain health: Getting ambitious about prevention from midlife’

We read with interest the recent ANZJP editorial ‘Optimising brain health: getting ambitious from midlife’, which explains the importance of early intervention to optimize age-related brain health (Lappin and Devenney, 2025). We wholeheartedly agree with Lappin and Devenney. Our only reservation would be their focus on Northern Hemisphere work, including cohorts from Denmark and the United Kingdom.

Australia and New Zealand have rich longitudinal study data that can inform this work, including world-class birth cohort studies. Birth cohorts are particularly powerful tools to disentangle the effect of risk factors that arise at different stages of the life course. Effective policy responses require an understanding of the causal structure of the outcome in question. This often means identifying complex mediation pathways in which early life exposures, such as childhood adversity and low educational attainment, lead to intermediate outcomes such as depression that in turn influence brain health in later life. Recent methodological advances, including target trial emulation, allow these complex causal relationships to be modelled more effectively with observational data.

New Zealand has two birth cohorts whose study members have now reached midlife. Study members from the Dunedin study are in their early 50s. The study has already made unique contributions to aging research through its Dunedin PACE tool, which quantifies the rate at which individuals biologically age by integrating longitudinal data across organ systems (Belsky et al., 2022). The study has progressively expanded to brain ageing measures, such as magnetic resonance imaging (MRI) and biomarkers of Alzheimer’s disease and dementia risk (Whitman et al., 2025). The Christchurch Health and Development Study is also approaching half a century and is shifting its attention towards age-related changes in mental health, cardiovascular disease and women’s reproductive health. Australia also has several mature cohorts, including the Mater University Pregnancy Study (est. 1982), the PATH cohort study (est. 1999) and the Longitudinal Study of Australian Children (est. 2004), and three that are now following next-generation offspring: the Australian Temperament Project & Generation 3 Study (est. 1983), the Raine Study (est. 1989) and the Victorian Adolescent and Intergenerational Cohort Studies (est. 1992).

Collectively, these longitudinal studies are well-placed to examine pathways to brain health and to inform prevention in midlife. To get the most value from their data, the studies must work strategically together. For example, Lappin and Devenney highlight perimenopause as a critical developmental phase for cognitive decline in women. Aggregating data from cohorts of different ages would increase the effective sample size and help generalizability across women of different ages, ethnic backgrounds and places. Cross-cohort collaborations would also provide more nuanced information about critical developmental windows for interventions such as hormonal treatments.

Current contestable funding models are often not a good fit for these studies due to their high infrastructure costs and their need to secure long-term funding beyond traditional grant funding cycles. The New Zealand Government has recognized this by placing the Dunedin Study and the Christchurch Health and Development Study under the auspices of its Strategic Science Investment Fund. Considering the value to Australia and New Zealand from collaborations between the studies, further consideration should be given to trans-national funding mechanisms to strengthen existing longitudinal research networks. This would also foster collective efforts in important areas such as brain health optimisation in later life.