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 The
data reviewed here illustrate that not all patients who report
insomnia are manifesting PSG sleep markers. An analogous observation
related to the symptom of dyspnea might be that the level of FEV1
does not match the severity of dyspnea reported. The absence of
expected physical corroboration, however, does not mean the symptom
is invalid. Actually, the use of combined PSG and self-report
sleep assessments allows for the characterization of insomnia
as a heterogeneous phenomenon, e.g. differentiation of insomnia
types along several dimensions of physiological sleep manifestations.
It is conceivable that there are varying contributing factors
to these sub-types and that they warrant different interventions.
Seeing such data should
raise further questions about scientific understandings. For example,
are those without clear PSG manifestations of insomnia in an earlier
phase or severity level? Do the physiological manifestations of
insomnia (i.e. PSG sleep impact) appear later in the trajectory
of chronic insomnia development but not in the early phases? With
time, if not treated or if the underlying drivers for insomnia
persist, will PSG manifestations of insomnia emerge? The development
of chronic or persistent insomnia manifestations longitudinally
has not been elucidated.
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