Ecological association between non-optimal ambient temperature and childhood developmental delay—a multi-country study

Introduction A research gap exists regarding the association between non-optimal ambient temperature (NOAT) and early childhood development (ECD) in low- and middle-income countries (LMICs). This study investigates the association between NOAT and early childhood developmental delay across five LMICs (Jordan, Kenya, Mozambique, the Philippines, and Tanzania). Methods Demographic and Health Survey data on ECD were combined with retrospective NASA temperature exposure using a case–control design. Exposure to monthly maximum temperatures was assigned to individual children aged 24–59 months ( n = 19,407). Exposure–lag–response associations were estimated using distributed lag non-linear models (DLNMs), conducted separately by country and adjusted for stunting. Subgroup analyses were performed for children aged 48–59 months, with outcomes analyzed by neural domains. Results In Jordan, Kenya, Mozambique, and Tanzania, NOAT (95th percentile) was associated with increased odds [aORs-3.21 (0.63–16.41); aOR-3.61 (3.07–4.25); aOR-1.69 (0.97–2.94) and aOR-1.71 (1.19–2.45)], respectively. In the Philippines, NOAT (5th-percentile) was associated with increased odds of developmental delay [cOR-1.45 (1.25–1.68)]. Among 48–59 months, NOAT (95th percentile) was associated with increased odds of delayed development at lags of 20 months [aOR-1.14 (1.08–1.21)]. In terms of the association of NOAT with learning outcomes, lag months of 21–40, temperatures at the 95th percentile were associated with higher odds of delayed learning (L 21 95th percentile cOR 1.01; 1.01, 1.01; L 40 95th percentile cOR 1.22; 1.15, 1.30). Conclusion The association between NOAT and ECD delay is of great importance for global development. Extreme weather events, such as heat events, will hinder the optimal development of children in low-income countries.