Fig. 1.

Structural equation model with pathways from each covariate to recurrent dry night cough (RNC). By convention, latent variables are depicted as ovals and rectangles represent indicator and other measured variables. For example, the latent variable wheeze is measured by the indicator variable wheeze at age one, wheeze at age two, and wheeze at age three. Solid lined arrows indicate significant associations and dashed lined arrows show associations that were not significant. Significant covariates are also shaded. The directions of the arrows distinguish between predictors and outcomes and do not necessarily imply causality.