As the population ages and life expectancy increases, policy-makers and citizens are concerned that our extra years should be healthy, productive, and enjoyable, not extra years of disease and disability. Finding new strategies to prevent age-related disease and disability requires identification of risk factors in early-to-midlife that can be ameliorated or reversed, well before the onset of age-related disease. This recognition lends new scientific significance to studies that have followed cohorts from childhood to midlife, including the Dunedin Study. The proposed work will use biomarker data collected from the same 1000 individuals at ages 26, 32, 38, and 45 to track the pace of their biological ageing. We will uncover why some people age faster than others, and why some fortunate people age more slowly than their age-peers. Findings are expected to support interventions to slow ageing, prevent age-related diseases, and enhance preparedness for wellbeing in later life.