The protective effect of housing affordability on childhood asthma risk: a longitudinal fixed-effects analysis.

Childhood asthma is influenced by early-life social conditions, yet few studies have evaluated housing affordability as a modifiable structural exposure. We used data from six biennial waves (2006-2018) of the Longitudinal Study of Australian Children to assess whether changes in housing affordability and rental assistance were associated with incident asthma in childhood. Fixed-effects logistic regression models were used to estimate within-child associations between time-varying housing exposure and asthma outcomes. The main analytic sample included 3773 children asthma-free at baseline; a subsample of 522 children in low-income renting households was used to evaluate rental assistance. Transitions into affordable housing were associated with a 31% reduction in asthma risk (OR, 0.69; 95% CI, 0.52-0.90). Among low-income private renters, new receipt of assistance was associated with 65% lower odds of asthma onset (OR, 0.35; 95% CI, 0.14-0.85). No associations were observed for asthma severity. Sensitivity analyses using lagged exposures, alternative definitions of affordability, and unadjusted income models yielded consistent findings. These findings support housing affordability as a potential policy lever for asthma prevention and demonstrate the utility of within-person designs for strengthening causal inference in observational evaluation of structural interventions.