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Table 2 Correlation between PSQI-total score and age, body mass index, traditional parameters of polysomnography, sleep questionnaire and scales, and saturation-related variables (n = 156)

From: More severe hypoxemia is associated with better subjective sleep quality in obstructive sleep apnea

Variables Correlation Lower 95 % Upper 95 % p-value
Demographic data     
 Age(years) 0.209 0.054 0.355 0.009*
 BMI (Kg/m2) 0.021 −0.137 0.177 0.796
Parameters of PSG     
 Total sleep time (min) −0.235 −0.379 −0.081 0.003*
 Sleep efficiency(%) −0.195 −0.342 −0.039 0.015*
 Sleep latency(min) 0.114 −0.044 0.267 0.156
 Stage I (%) 0.050 −0.108 0.206 0.533
 Stage II (%) 0.001 −0.156 0.158 0.992
 Stage III (%) −0.077 −0.231 0.081 0.339
 Stage REM (%) −0.016 −0.172 0.142 0.846
 AHI (/hour) −0.113 −0.265 0.045 0.162
 Mean SpO2 (%) 0.016 −0.142 0.172 0.846
 Mini SpO2 (%) 0.084 −0.075 0.238 0.300
 ODI (/hour) −0.085 −0.239 0.073 0.291
 T90 (second/hour) −0.069 −0.223 0.090 0.396
 Arousal index (/hour) −0.023 −0.179 0.135 0.778
 PLMI (/hour) 0.146 −0.011 0.296 0.069
Questionnaire     
 ESS 0.274 0.122 0.413 <0.001*
 SF-36 physical −0.394 −0.519 −0.253 <0.001*
 SF-36 mental −0.445 −0.563 −0.310 <0.001*
 CESD (n = 36) 0.372 0.049 0.624 0.026*
 HADS-depression (n = 120) 0.257 0.081 0.418 0.005*
Saturation-related parameters     
 Median SpO2 −0.096 −0.249 0.062 0.235
 Lowest 5 % SpO2 0.115 −0.043 0.267 0.154
 Highest 5 % SpO2 −0.149 −0.299 0.008 0.063
 Highest % SpO2 minus 0.051 −0.107 0.206 0.526
 Median SpO2
 Median SpO2 minus Lowest 5 % SpO2 −0.161 −0.310 −0.004 0.045*
  1. *p < 0.05
  2. Abbreviations: BMI body mass index; REM rapid eye movement sleep; AHI apnea-hypopnea index; Mean SpO2 mean saturation of total time in bed; Mini SpO2 minimum saturation of total time in bed; ODI oxygen desaturation index; T90 time spent with saturation < 90 %; PLMI periodic leg movement index; ESS Epworth sleepiness scale; SF-36 Physical physical component score of short form 36; SF-36 Mental mental component score of short form 36; CESD center for epidemiologic studies depression scale; HADS-depression depression component of Hospital Anxiety and Depression Scale; median SpO2 the median value of saturation of total sleep time; Lowest 5 % SpO2 averaged value from the lowest 5 % saturation of total sleep time; Highest 5 % SpO2 averaged value from the highest 5 % saturation of total sleep time; Highest% SpO2 minus Medium SpO2 the difference between Highest 5 % SpO2 and Medium SpO2; Median SpO2 minus Lowest 5 % SpO2 the difference between Median SpO2 and Lowest 5 % SpO2