Can Successful Early Childhood Interventions Sustain Impacts into Middle Childhood? A test from Kenya - Abstract An estimated 43 percent of children under age 5 in low- and middle-income countries (LMICs) will not reach their full developmental potential due to poverty, stunting, or inadequate psychosocial stimulation. Parenting interventions that coach parents on responsive caregiving can effectively improve ECD outcomes in LMICs, at least in the short-term. However, the very few programs that have examined their sustained effects find that early program impacts tend to fade over time. To date, the only parenting interventions demonstrating sustained impacts five or more years after the end of their programs from a LMIC are two small pilot studies, both featuring weekly individual home visits over two years on a total of 134 stunted or low birthweight children from urban Kingston, Jamaica. Such intensive delivery models are prohibitively expensive to scale in rural and resource-poor LMIC settings. Community-based group meetings are a more cost-effective and scalable delivery model, and can also allowforpeer-to-peer learning and the formation of social support networks. Though growing evidence from LMICs shows that group meetings are at least as effective as individual home visits to improve ECD in the short- term, evidence on their ability to sustain impacts over time, and the mechanisms underlying such impacts (e.g., social support), is still very limited. With NICHD support (R01HD090045), we demonstrated that an 8-month, group-based ECD parenting intervention delivered by CHWs in rural Kenya significantly improved short-term ECD outcomes and parenting practices, and the program was highly cost-effective. In complementary work (R21HD098508), immediately after the main intervention, in half of intervention villages, we added 9 bi-monthly “booster” group meetings to reinforce key messages over two years. In a recent two-year follow-up assessment, we found that early impacts from the original 8-month intervention were sustained when children were ages 3.5 to 5, and the poorest families benefited the most. The booster extension, despite being severely disrupted by the COVID- 19 pandemic, had small additive effects on children’s socioemotional outcomes and parenting behaviors. Building on these results, we now propose to follow-up our original study cohort roughly 5 years after the end of the intervention to measure longer-term sustained impacts on our sample of targeted children who will be roughly 6.5 to 8 years old, as well as their younger and older siblings to uncover potential spillover effects. We will re-enroll households from our original sample across 60 villages to collect an additional survey wave to measure children’s cognitive, language, executive function and socio-emotional skills, as well as parenting behaviors, knowledge and beliefs, social networks, and social norms around parenting to examine potential mediating pathways driving any sustained impacts and any spillover impacts onto siblings. The goal of our study is to help fill a gap regarding evidence on the long-term effectiveness of ECD programs on children’s outcomes from a scalable and cost-effective model of delivery to help inform policy.