Area-level determinants and social inequities in early developmental delay: A scoping review

Background

Early childhood developmental delays (CDD) are a public health concern linked to lower health across the life course. Family socioeconomic position (SEP) is a well-established determinant, while the role and mechanisms of area-level factors–including natural and built environment, deprivation, and social networks–remain insufficiently understood. Guided by life course and social equity perspectives, this review maps evidence on area-level factors and CDD, including study designs, measures, theoretical frameworks, and how SEP is addressed.

Methods

Following PRISMA-ScR guidelines, four databases were systematically searched, complemented by reference screening, citation tracking, and website searches. Results were summarized descriptively.

Results

34 studies were included, mainly cohort designs (n = 31). Most examined behavioural (n = 23), and cognitive delay (n = 8), using validated instruments. CDD were assessed from infancy to age 7, most often between 3 to 5. Across 267 analyses, air pollution (54%) and area deprivation (18%) were most studied, typically measured during pregnancy or the first year of life. Area-level factors were measured directly (81%), while proxy or self-reported measures were less common. SEP was included for adjustment (81%), with limited examination of interaction or stratification. Reported frameworks included ‘Developmental Origins of Health and Disease’, social determinants of health and allostatic load.

Conclusions

Heterogeneity exists in populations and exposure assessment. Evidence suggests that area-level factors are associated with CDD, underscoring the importance of early-life context for health inequalities. Consistent with life course models, the reported frameworks may inform future research. Gaps include limited attention to preconception, temporal dynamics, intergenerational processes, and mechanisms related to SEP. Challenges in establishing causality persist, mainly due to selection bias and temporal confounding.

Key messages

• Evidence suggests that area-level factors are associated with early life development, therefore early childhood may be a sensitive period for context-related health inequalities.

• Studies should expand exposure assessment to preconception and capture temporal dynamics in the relationship between area-level factors, developmental delays, and individual-level SEP.