Time trends and area-level socioeconomic inequalities in early childhood development at 2-2.5 years old in England between 2019 and 2025: a local area ecological study.

Introduction: There are gaps in national data on early childhood development to inform progress in closing the inequality gap and to capture the impact of the COVID-19 pandemic on children's development in different developmental domains. This longitudinal area-level ecological study examined time trends in socioeconomic inequalities in early childhood development at 2-2.5 years in England's local authorities between 2019 and 2025. Methods: We included 2 105 384 children from 119 upper-tier local authorities. Rates per 100 children not on track in development at 2-2.5 years, assessed on the Ages and Stages Questionnaire 3, were analysed. Area-level income deprivation was assessed using the Income Deprivation Affecting Children Index 2019, converted to the Slope Index of Inequality (SII) and Relative Index of Inequality (RII). Linear mixed-effect models assessed the fixed effects of year, year Results: The average rate of children not on track in any developmental domain increased from 15.2 (95% CI 13.7 to 16.7) in 2019, peaking in 2023 (19.1 (17.5 to 20.7)), but with little sign of recovery by 2025 (year: 1.09 (1.05 to 1.13); year Discussion: In England, early childhood development worsened during the pandemic and children born after the pandemic continue to be affected. Area-level inequalities were striking but did not worsen during this period. Pandemic-recovery efforts need to consider the potentially enormous economic and societal cost of disruption to early childhood development.