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Table 6 Convergent validity as assessed by correlations between two questions related to sleep from the General Health Questionnaire (GHQ) and the Pittsburgh Sleep Quality Index (PSQI) for the TMD cases sample (N = 609)

From: Exploration of dimensionality and psychometric properties of the Pittsburgh Sleep Quality Index in cases with temporomandibular disorders

GHQ question N PSQI global score(mean) PSQI global score (SD) Spearman’s rho (95% CI), and a level of significance
Have you recently lost much sleep over worry?     0.43 (0.36 to 0.49)*
Not at all 296 5.4 3.4  
No more than usual 239 8.1 3.8  
Rather more than usual 63 9.6 4.0  
Much more than usual 11 12.5 2.7  
Have you recently had difficulty in staying asleep?     0.48 (0.42 to 0.54)*
Not at all 288 5.1 2.8  
No more than usual 211 7.9 3.9  
Rather more than usual 94 10.1 4.1  
Much more than usual 16 11.8 2.9  
  1. *P < 0.001.