In addition to sleep problems being common in this
population, our study found that sleep problems were
positively associated with functional disability, as
expected. However, mixed results were found with regard
to the role of physical and emotional symptoms as
proposed mediators of this relationship. Sleep problems
predicted both emotional and physical symptoms in our
causal model, but only physical symptoms had a direct
impact on functional disability. In fact, physical symptoms
fully mediated the relationship between sleep problems
and problems in daily function. This finding,
initially based on the estimated frequency of missed
school and other activities, was replicated using the
more subjective perception of functional disability
afforded by the FDI.