Table 3.

Association between sleep disturbance and cognitive dysfunction among 98 subjects with COPD^*

	Difference in Z-score associated with presence of sleep disturbance (95% CI)†	P-value for difference
Memory
Hopkins Verbal Learning Test	−0.62 (−1.13 to −0.11)	0.018
Executive Function
Stroop Color Word Test	−0.26 (−0.72 to 0.19)	0.26
Phonemic Fluency Test	−0.23 (−0.66 to 0.20)	0.30
DKEFS Trail Making Test	0.05 (−0.45 to 0.55)	0.86

Z-scores are standardized for age, based on a healthy referent population. A Z-score of 0 is the mean score for age while a Z-score of −1.0 is one standard deviation below the mean (i.e. one standard deviation lower cognitive function).

^*Each of the four cognitive function variables listed above was used as an outcome (dependent variable) in its own multivariable linear regression analysis in which sleep disturbance (present vs absent) was an independent variable. All analyses controlled for gender, race, marital status, educational attainment, and BMI. (Z-scores are already adjusted for age).

^†Mean difference in Z-score associated with the presence of sleep disturbance, relative to absence of sleep disturbance.