The Association Between Cognitive Functions and Psychological Factors in Patients with Severe COPD

Figures & data

Table 1 Baseline Characteristics of Patients with COPD and Age-Matched Controls

	COPD Patients (n=80)	Controls (n=22)	p
Age (yrs), mean (SD)	64 (7)	61 (9)	0.13
Sex (male), n (%)	42 (53)	7 (32)	0.09
Cohabitation, n (%)
Living alone	27 (34)	1 (5)	<0.01
Living with partner	53 (66)	21 (95)
Years of education, mean (SD)	12 (3)	15 (3)	<0.01
Employment status, n (%)
Not working	21 (26)	0 (0)	<0.01
Working	22 (28)	12 (55)
Pensioner	37 (46)	10 (45)
Smoking, n (%)
Smoker	30 (37)	1 (5)	<0.001
Former	50 (63)	9 (41)
Never	0 (0)	12 (54)
FEV1, % predicted, mean (SD)	35 (8)	99 (11)	<0.001
mMRC (0–4), median (IQR)	2 (2–3)	0 (0–0)	<0.001
CAT score (0–40), mean (SD)	18 (7)	–
Obstructive Sleep Apnea and/or ND, n (%)	56 (70)	6 (27)	<0.001
ESS (0–24), mean (SD)	5 (3)	4 (2)	0.05
Charlson Comorbidity Index Score, median (IQR)	1 (1–2)	0 (0–0)	<0.001
Mental health disorder, n (%)	10 (13)	1 (5)	0.29
HADS (0–42), mean (SD)	8 (6)	2 (2)	0.00
HADS-Anxiety (0–21), mean (SD)	5 (4)	2 (2)	<0.001
HADS-Depression (0–21), mean (SD)	3 (3)	1 (1)	0.00
PSS (0–40), mean (SD)	12 (7)	4 (3)	0.00

Notes: Continuous variables are specified as mean (SD) and categorical variables as number (%). mMRC and Charlson Comorbidity Index Score are not normal distributed and therefore we use median (IQR). Using parametric unpaired t-test for continuous normally distributed data. Using nonparametric Mann Whitney U-test for not normal distributed data. Using Chi-squared test for categorical data.

Abbreviations: FEV₁, Forced Expiratory Volume in 1 second, % of predicted; mMRC, modified Medical Research Council dyspnea scale; CAT score, COPD Assessment Test score; ND, Nocturnal Desaturation; ESS, Epworth Sleepiness Scale; HADS, Hospital Anxiety and Depression Scale; PSS, Perceived Stress Scale.

Figure 1 Study flowchart of the inclusion process.

Abbreviations: FEV_1, Forced Expiratory Volume in 1 second, % of predicted; OSA, Obstructive Sleep Apnea.

Table 2 Characteristics of Patients with COPD with CI (MoCA Score <26) and without CI (MoCA Score 26–30)

	CI (n=32)	No CI (n=48)	p
Age (yrs), mean (SD)	67 (8)	62 (6)	<0.01
Sex (male), n (%)	15 (47)	27 (56)	0.41
Cohabitation, n (%)
Living alone	9 (28)	18 (38)	0.39
Living with partner	23 (72)	30 (62)
Years of education, mean (SD)	12 (3)	13 (3)	0.02
Employment status, n (%)
Not working	7 (22)	14 (29)	<0.01
Working	3 (9)	19 (40)
Pensioner	22 (69)	15 (31)
Smoking, n (%)
Smoker	12 (38)	18 (38)	1.00
Former	20 (62)	30 (62)
Never	0 (0)	0 (0)
FEV1, % predicted, mean (SD)	36 (8)	34 (9)	0.27
mMRC (0–4), median (IQR)	4 (3–4)	3 (2–4)	0.02
CAT score (0–40), mean (SD)	19 (6)	16 (7)	0.047
Obstructive sleep apnea and/or ND, n (%)	20 (63)	36 (75)	0.23
ESS (0–24), mean (SD)	5 (3)	5 (3)	0.89
Charlson Comorbidity Index Score, median (IQR)	1 (1–2)	1 (1–2)	0.65
Mental health disorder, n (%)	3 (9)	7 (15)	0.49
HADS (0–42), mean (SD)	9 (6)	8 (6)	0.40
HADS-Anxiety (0–21), mean (SD)	6 (4)	5 (4)	0.31
HADS-Depression (0–21), mean (SD)	3 (3)	3 (3)	0.66
PSS (0–40), mean (SD)	13 (7)	12 (8)	0.37

Notes: Continuous variables are specified as mean (SD), not normally distributed variables as median (IQR) and categorical variables as number (%). Using parametric unpaired t-test for normally distributed data. Using nonparametric Mann Whitney U-test for not normally distributed data. Using Chi-squared test for categorical data.

Abbreviations: CI, cognitive impairment; MoCA, Montreal Cognitive Assessment; FEV₁, Forced Expiratory Volume in one second, % of predicted; mMRC, modified Medical Research Council dyspnea scale; CAT score, COPD Assessment Test score; ND, Nocturnal Desaturation; ESS, Epworth Sleepiness Scale; HADS, Hospital Anxiety and Depression Scale; PSS, Perceived Stress Scale.

Table 3 Hierarchical Multiple Regression Analyses – Associations of Sociodemographic, Physical and Self-Perceived COPD Symptoms as Well as Psychological Factors and Cognitive Functions in Patients with COPD

		Cognitive Outcome Variables
		Cognitive Impairment (MoCA Score)					Attention (CRT-Index)					Perception and Attention (SD from Center of the Road)					Perception and Attention (Average Response Time in Sec.)
		n=80					n=80					n=78					n=78
Model	Predictors	β	p	R^2	ΔR^2	p	β	p	R^2	ΔR^2	p	β	p	R^2	ΔR^2	p	β	p	R^2	ΔR^2	p
Step 1				0.156^a	-	-			0.140^a	-				0.394^b	-				0.239^b	-
	Age	−0.099	<0.01				0.006	0.57				1.079	0.00				1.030	0.00
	Sex (reference female)	0.173	0.72				0.449	<0.01				0.267	0.00				0.815	0.03
	Years of education	0.185	0.03				0.039	0.13				0.934	0.10				1.005	0.75
	Constant term	29.908					0.947					0.027					0.453
Step 2				0.175^c	0.019	0.63			0.155^c	0.015	0.7			0.408^b	0.014	0.60			0.253^a	0.014	0.68
	Age	−0.088	0.01				0.004	0.72				1.076	0.00				1.029	0.00
	Sex (reference female)	0.206	0.67				0.459	<0.01				0.275	0.00				0.817	0.04
	Years of education	0.193	0.02				0.036	0.18				0.933	0.10				1.005	0.75
	FEV1, % predicted	−0.013	0.67				0.005	0.58				1.018	0.22				1.003	0.61
	Currently smoker (reference no smoking)	0.532	0.33				−0.043	0.80				0.956	0.87				0.978	0.84
	Sleep apnea (reference no OSA and/or ND)	0.440	0.42				0.149	0.39				0.950	0.85				0.899	0.33
	Constant term	29.005					0.835					0.019					0.460
Step 3				0.191^c	0.016	0.20			0.168	0.013	0.26			0.416^b	0.008	0.30			0.302^b	0.049	0.02
	Age	−0.087	0.01				0.004	0.69				1.076	0.00				1.028	0.00
	Sex (reference female)	0.132	0.79				0.438	<0.01				0.267	0.00				0.838	0.07
	Years of education	0.167	0.054				0.028	0.30				0.923	0.07				1.015	0.37
	FEV1, % predicted	−0.025	0.42				0.001	0.88				1.013	0.42				1.008	0.21
	Currently smoker (reference no smoking)	0.695	0.22				0.003	0.99				1.022	0.94				0.921	0.46
	Sleep apnea (reference no OSA and/or ND)	0.503	0.36				0.167	0.33				0.971	0.91				0.881	0.23
	CAT score	−0.049	0.23				−0.014	0.28				0.980	0.33				1.017	0.03
	Constant term	30.480					1.254					0.034					0.273
Step 4				0.208	0.017	0.63			0.256^c	0.088	0.03			0.437^b	0.021	0.43			0.332^a	0.03	0.33
	Age	−0.093	0.01				0.0003	0.98				1.078	0.00				1.028	0.00
	Sex (reference female)	0.216	0.67				0.440	<0.01				0.282	0.00				0.820	0.047
	Years of education	0.165	0.059				0.026	0.32				0.924	0.07				1.014	0.40
	FEV1, % predicted	−0.036	0.28				0.003	0.79				1.014	0.39				1.010	0.13
	Currently smoker (reference no smoking)	0.798	0.18				−0.037	0.83				1.061	0.84				0.893	0.32
	Sleep apnea (reference no OSA and/or ND)	0.512	0.36				0.232	0.17				1.008	0.98				0.890	0.27
	CAT score	−0.059	0.22				−0.001	0.92				0.975	0.28				1.022	0.02
	HADS-Anxiety	0.003	0.98				0.060	0.10				1.094	0.13				1.011	0.64
	HADS-Depression	−0.166	0.27				−0.030	0.50				0.968	0.64				1.028	0.33
	PSS	0.046	0.43				−0.041	0.02				0.978	0.45				0.981	0.10
	Constant term	31.234					1.522					0.027					0.258

Notes: ^ap<0.01, ^bp<0.001, ^cp<0.05. Results from hierarchical regression analysis depicting the contribution of mental health to cognitive functions. In a stepwise regression, sociodemographic were controlled for in the first model. In the second model, physical variables were added, and self-perceived COPD symptoms were added in the third model. In the final model, mental health were added. Models explained variances are reported as R² and ΔR², which are the difference in R² between the steps. Using Likelihood-ratio test to examine significance level of ΔR². Driving outcome variables are not normally distributed and therefore regression analyses are made with log-transformed data but coefficients are back transformed via exponential function.

Abbreviations: MoCA, Montreal Cognitive Assessment; CRT-index, Continuous Reaction Time Index; SD, standard deviation; FEV₁, Forced Expiratory Volume in one second, % of predicted; OSA, Obstructive Sleep Apnea; ND, nocturnal desaturation; CAT score, COPD Assessment Test score; HADS, Hospital Anxiety and Depression Scale; PSS, Perceived Stress Scale.