Eight decades of follow-up link life course exposures to proteomic organ ageing and longevity.

The pace of organ ageing varies substantially between individuals, yet drivers of variability remain poorly understood. This gap is critical, given only 20-30% of longevity is genetically inherited1,2 and age-related diseases are leading causes of morbidity and mortality3. Proteomic clocks allow organ ageing to be estimated from blood sampling4, facilitating study of how life course exposures shape biological ageing heterogeneity. Here, we leverage the unique design of the MRC National Survey of Health and Development (NSHD), the world's oldest continuously followed birth cohort, to track 1,803 individuals across eight decades since birth in 1946. At mean age 63.2 years, we estimated proteomic ageing in seven organs. Despite near identical chronological ages, participants' proteomes revealed biological ageing disparities spanning decades. Extreme ageing in multiple organs was a strong prognostic indicator for all-cause mortality over the following 15 years (HR=6.62 for ≥ 4 extremely aged organs). Adversity and being overweight in adolescence associated with accelerated ageing decades later in life. Completing secondary school education and maintaining physical activity linked to relative biological youth. Mediation analyses indicated liver, kidney and immune ageing linked life course exposures to mortality. Across 10,776 plasma protein targets, we identified 143 predictors of longevity, including MED9, strongly linked to diverse socio-behavioural exposures. These findings provide unique insights into which factors are likely to shape how we age, when in life they may be influential, and how biological effects emerge, informing healthy ageing promotion.