Background Early-childhood socioeconomic and health disadvantages are detrimental for long-term health and wellbeing. However, it is challenging to develop a robust economic case for investment in early years because it is hard to estimate the full range of long-term effects and cost savings that can accumulate decades into the future. To address this, we develop the first detailed childhood microsimulation model based on bespoke modelling of Millenium Cohort Study (MCS) that can quantify such long-term health and wellbeing consequences, the associated public costs and impact on inequalities.

Methods We model key exposures and outcomes between ages 0-17 of a birth-cohort of 15,000 children. We choose early-years exposures often targeted by policy interventions: having a teenage mother, preterm birth, low birthweight (for gestational age), low height (age 3); activity limiting condition (age 3), school readiness (age 5), household income and poverty (ages 0 to 5). Based on decision rules and Directed acyclic graphs (DAGs), we then run regressions to predict causal effects of exposures on outcomes during ages 7-17. We use outcomes at age 17 to link to an existing discrete event simulation model LifeSim Adulthood to model life outcomes and costs in adulthood. We quantify the long-term health and wellbeing, and public costs associated with childhood disadvantages (our list of exposures). We assess the robustness of our findings to variation in key modelling assumptions using sensitivity analysis.

Results We here report results up to age 17 for just one exposure: teenage pregnancy (we will have results for all exposures by June 2024). We find teenage pregnancy increases the incidence of adverse child outcomes at age 17 (reported as increase in cases per 100,000 17-year olds in the UK [CI]): regular smoking (1,500 [1,343-1,657]), bad GCSEs (2,000 [1,905-2,095]), obesity (600 [550-650]), poor health (800 [700-900]), psychological distress (2,100 [1,990-2,210]). It is estimated to generate an additional £1,170 [1,297-1,506] cost per child in the general population with the following breakdown by cost-bearing outcome: hospitalisation (£586 [564-608]), conduct problems (£192 [188-196]), activity-limiting conditions (£172 [167-177]), special educational needs (£134 [166-152]), permanent school exclusion (£69 [62-76]).

Conclusion Our model helps to build an economic case for investment in early years. We will report results for all eight exposures at the SSM meeting, including a ready reckoner table of long term benefits and costs of reducing each childhood disadvantage.