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For most people,
perceived sleep quality is related to perceptions of how long
it takes to fall asleep and perceived number and duration of awakenings
during the night (Baker
et al., 1999). As already mentioned, a close connection of
perceived sleep quality and PSG data regarding the sleep pattern
is not always evident. Inquiry into the connection between the
two creates its own set of research intrigues. Consider the following
example.
Scenario:
We (Shaver and colleagues) conducted a study on insomnia in midlife
women (40 -59 years old), a time of reproductive hormonal fluctuations
and when cross-sectional survey data has shown a steep increase
in the prevalence of insomnia. We selected women from the community
reporting insomnia but denying any major physical or mental illness.
We did PSG recordings on 81 women reporting insomnia as well as
30 control women in their homes for 5 consecutive nights. Following
analysis, we discovered that not all women reporting insomnia
had low sleep efficiencies.
Using these
data, we developed cutoff criteria and then classified the insomnia
women into two groups. One group incorporated 33 women who had
consistently low sleep efficiency, using a criterion of having
at least 3 nights of PSG sleep efficiency of < 85%. These women
were classed as having psychophysiological-type insomnia
(positive self-report of insomnia and physiological corroboration
of low sleep efficiency). However, 18 women who reported insomnia
had no nights of low PSG sleep efficiency (<85%) and moreover,
had at least three nights of PSG sleep efficiency > 88%. We
classed them as having no objective insomnia. These data
indicate that some women, although perceiving insomnia, did not
have low sleep efficiencies as shown on PSG records. The obvious
question is: what creates the difference? Answers may lie both
in the realms of methodology and interpretations. Furthermore,
the remaining 30 women reporting insomnia did not meet the chosen
criteria to be classified distinctly into either of these groups.
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