title: Validity of 2 sleep quality items to be used in a large cohort study of kidney transplant recipients.
abstract: BACKGROUND
  Poor sleep quality and poor daytime functioning affect many kidney transplant patients.
  
  
  OBJECTIVE
  To evaluate the validity of 2 items assessing sleep quality and daytime functioning using the Pittsburgh Sleep Quality Index as reference standard before use in a large cohort study, following the American Psychological Association's guidelines.
  
  
  METHODS
  A cross-sectional study using a psychosocial questionnaire developed for a large cohort study and the Pittsburgh Sleep Quality Index.
  
  
  METHODS
  One hundred thirty-five home-dwelling kidney transplant patients aged 21 to 76 years (mean, 51.6 years; SD, 11.9 years).
  
  
  METHODS
  Evidence on content, internal structure, and relation to other variables.
  
  
  RESULTS
  The Pittsburgh Sleep Quality Index indicated a 47.4% prevalence of poor sleep quality; the sleep quality item in the psychosocial questionnaire showed a 30.7% prevalence of poor sleep quality and a 34.1% prevalence of poor daytime functioning. Content validity was good for the psychosocial questionnaire's sleep quality item but poor for its daytime functioning item. As hypothesized, the psychosocial questionnaire's sleep quality item was moderately correlated with its daytime functioning item (Spearman rho, p(s) = 0.520, P<.001), indicating related but distinct concepts. When combined, the 2 items from the psychosocial questionnaire showed significant correlations with the total score on the Pittsburgh Sleep Quality Index (p(s) = -0.784, P < .001), depressive symptoms (p = -0.680, P < .001), perceived health status (p(s) = 0.619, P<.001), and subjective health status (p(s) = 0.671, P<.001) in the expected directions.
  
  
  CONCLUSIONS
  For kidney transplant patients, validity is strong for the psychosocial questionnaire's sleep quality item, but the mixed findings regarding the validity of the daytime functioning item suggest that additional items are needed to measure daytime functioning.
authors.affiliation: University of Basel, Center for Chronobiology, Switzerland.
authors.forename: Hanna
authors.initials: H
authors.lastname: Burkhalter
authors.forename: Susan M
authors.initials: SM
authors.lastname: Sereika
authors.forename: Sandra
authors.initials: S
authors.lastname: Engberg
authors.forename: Anna
authors.initials: A
authors.lastname: Wirz-Justice
authors.forename: Jürg
authors.initials: J
authors.lastname: Steiger
authors.forename: Sabina
authors.initials: S
authors.lastname: De Geest
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012372:ROC Curve; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000175:diagnosis* / Q000453:epidemiology; D011795:Surveys and Questionnaires