Table 5

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

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**


*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.

Li et al. Arthritis Research & Therapy 2012 14:R215   doi:10.1186/ar4054

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