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Table 5 Correlation coefficients between components of PSQI, demographic, clinical, and psychogenic variables (Spearman rho)

From: Sleep disturbances are associated with increased pain, disease activity, depression, and anxiety in ankylosing spondylitis: a case-control study

Variables PSQI Subjective sleep quality Sleep latency Sleep duration Habitual sleep efficiency Sleep disorders Use of sleep medications Daytime dysfunction
Age (years) 0.165** 0.073 0.142* 0.074 0.065 0.193** 0.135* 0.139*
Years of education -0.149** 0.003 -0.206** -0.083 -0.119* -0.047 -0.186** -0.099
ESR (mm/h) 0.163** 0.187** 0.086 0.070 0.171** 0.102 0.062 0.044
CRP (mg/dl) 0.164** 0.172** 0.072 0.034 0.159** 0.134* 0.040 0.125*
Disease duration (years) 0.094 0.051 0.091 0.011 -0.013 0.095 -0.014 0.133*
Morning stiffness (minutes) 0.250** 0.219** 0.185** 0.103 0.177** 0.173** 0.069 0.180**
Fingertip-to-floor distance (cm) 0.04 0.040 0.010 -0.038 -0.025 0.084 0.049 0.114*
Overall assessment of health (VAS) 0.386** 0.258** 0.241** 0.073 0.200** 0.359** 0.174** 0.375**
Nocturnal pain (VAS) 0.487** 0.324** 0.337** 0.181** 0.330** 0.364** 0.129* 0.388**
Total back pain (VAS) 0.485** 0.319** 0.297** 0.199** 0.295** 0.386** 0.176** 0.424**
BASMI 0.093 0.044 0.057 0.023 0.105 0.122* 0.025 0.065
BASDAI 0.479** 0.322** 0.327** 0.130** 0.214** 0.421** 0.206** 0.467**
BASFI 0.312** 0.198** 0.168** 0.052 0.119* 0.421** 0.128* 0.313**
SDS 0.467** 0.290** 0.346** 0.124* 0.178** 0.438** 0.167** 0.448**
SAS 0.522** 0.347** 0.384** 0.173** 0.236** 0.493** 0.169** 0.439**
  1. * P < 0.05; ** P < 0.01. Spearman rho, <0.3, the weak correlation; Spearman rho, 0.3 to 0.5, the medium correlation; Spearman rho, >0.5, the high correlation. BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASMI, Bath Ankylosing Spondylitis Metrology Index; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; PSQI, Pittsburgh Sleep Quality Index; SAS, Self-rating Anxiety Scale; SDS, Self-rating Depression Scale; VAS, visual analogue scale.