Cardiorespiratory fitness (CRF) is a modifiable cardiovascular risk factor for children and adults. However, little is known how variations in CRF across the life course impact long-term cardiovascular health. Therefore, we examined how CRF from childhood to mid-adulthood associates with the American Heart Association's (AHA) Life's Essential 8 (LE8), a measure of overall cardiovascular health.

As part of the longitudinal Childhood Determinants of Adult Health Study, 240 participants had their CRF measured as physical work capacity at 170 beats per minute (PWC₁₇₀) in childhood (1985: 9, 12, 15 years), young adulthood (2004-06: 26-36 years), and mid-adulthood (2014-19: 36-49 years). In mid-adulthood, diet, physical activity, smoking, sleep, body mass index, blood lipids, blood glucose and blood pressure was assessed, with LE8 scores created following AHA recommendations. Associations were examined using linear regression and the Bayesian relevant life course model. The relationship between CRF across the life course and adult LE8 was best characterised by a lifetime growth model, where higher childhood CRF (β = 3.48, 95%CI = 1.36-5.60), and increased CRF between childhood and young adulthood (β = 3.64, 95%CI = 2.12-5.17) and between young and mid-adulthood (β = 4.15, 95%CI = 2.23-6.06) were positively associated with LE8 in midlife. When the relative importance of CRF within this relationship was quantified, CRF was important at each examined life stage, with a sensitive period in midlife.

These findings support a life course approach to the prevention of adverse cardiovascular health, highlighting the cardiovascular benefits of higher CRF in both childhood and adulthood, and increasing CRF over time.