Since its introduction in 1989, the Pittsburgh Sleep
Quality Index (PSQI) has gained widespread acceptance
as a useful tool to measure sleep quality in different patient
groups (for overview of sleep questionnaires, see Refs).
Its good reliability and validity could be shown for patients
with psychiatric and sleep disorders, for patients with
different somatic diseases, for nursing home residents
, and for healthy elderly subjects , whereas data on its
validity and reliability for primary insomnia are scarce.