Child health and social care outcomes in large households: a population-based linked-data study in Northwest London.

Introduction: Children in larger households in the UK are at increased risk of poverty due to policies such as the two-child benefit limit, but evidence on their health and social care outcomes is limited. We used linked administrative data to examine whether outcomes differ between children in smaller (1-2 children) and larger (≥3 children) households in Northwest London (NWL). Methods: We conducted a retrospective, population-based study using the Discover-NWL database (2005-2024). Outcomes included dental extraction (at <12 years of age), antidepressant prescription, emergency hospital admission (respiratory and any cause), emergency department (ED) visit and Child in Need (CiN) status. Analyses were descriptive and stratified by Index of Multiple Deprivation quintiles; multilevel logistic regression adjusted for age, sex, ethnicity, deprivation and within-household clustering. Results: Data were available on 477 602 children aged 0-18 years. In unadjusted descriptive analyses, children in larger households had higher population-level rates of dental extraction, respiratory admissions and CiN status, and lower rates of ED visits and antidepressant prescribing.In adjusted multilevel models, larger household size was associated with higher odds of dental extraction (OR 1.07 per additional child, 95% CI 1.05 to 1.10) and CiN status (OR 2.90, 95% CI 2.77 to 3.04), and lower odds of antidepressant prescribing (OR 0.86, 95% CI 0.82 to 0.90) and ED visits (OR 0.94, 95% CI 0.93 to 0.95). Conclusion: Children in larger households experience different patterns of health and social care contact compared with those in smaller households. These population-level findings, supported by adjusted analyses, provide new evidence on household size as a marker of child health and social care inequalities and may inform future research and policy.