A 1-year follow-up study exploring the associations between perception of illness and health-related quality of life in persons with chronic obstructive pulmonary disease

Figures & data

Figure 1 The explored associations between the study variables.

Abbreviation: COPD, chronic obstructive pulmonary disease.

Table 1 The scoring of items measuring self-reported level of activity

Response category	Hours per week
	None	<1	1–2	≥3
Low-level activity (not sweaty/breathless)	0	1	2	3
High-level activity (sweaty/breathless)	0	2	3	4

Notes: The question read as follows: “How much physical activity do you have in leisure time? Travel to work is regarded as leisure. State approximately how many hours per week you are physically active. Choose a number of hours that may apply to a typical week last year.”

Table 2 Characteristics of men and women in the sample at baseline (N=60)

Characteristic	All (N=60)	Men (n=36)	Women (n=24)	ES	P
Sociodemographic
Age – years (M/SD)	65.4 (8.7)	65.8 (8.7)	64.9 (8.8)	0.10	0.69
Education >12 years	17 (28.3)	10 (27.8)	7 (29.2)		0.91
Living in relationship (n/%)	41 (68.3)	27 (75.0)	14 (58.3)		0.17
Working (n/%)	14 (23.3)	10 (27.8)	4 (16.7)		0.37
Social support (M/SD)	4.3 (0.7)	4.4 (0.6)	4.2 (0.9)	0.26	0.26
Health behavior	(M/SD)	(M/SD)	(M/SD)
Physical activity (0–4)	1.4 (0.9)	1.4 (1.0)	1.3 (0.7)	0.12	0.40
Illness perceptions
Consequences (0–10)	5.9 (2.3)	5.5 (2.3)	6.5 (2.2)	−0.44	0.09
Timeline (0–10)	9.6 (1.2)	9.8 (0.6)	9.3 (1.7)	0.39	0.18
Personal control (0–10)	5.1 (2.1)	4.6 (2.1)	5.8 (2.3)	−0.54	0.04
Treatment control (0–10)	6.6 (2.5)	6.4 (2.4)	6.9 (2.7)	−0.20	0.48
Identity (0–10)	6.3 (1.9)	6.1 (1.9)	6.6 (2.0)	−0.26	0.31
Concern (0–10)	5.4 (2.5)	5.2 (2.7)	5.7 (2.2)	−0.20	0.47
Understanding (0–10)	7.0 (2.2)	6.4 (2.2)	7.9 (1.8)	−0.75	<0.01
Emotional response (0–10)	4.5 (2.6)	4.5 (2.6)	4.5 (2.7)	0.00	0.97
Self-perceptions
Self-efficacy (10–40)	28.5 (5.4)	28.1 (5.2)	29.0 (5.9)	−0.16	0.50
Quality of life
PCS (0–100)	33.3 (11.2)	33.8 (10.7)	32.7 (12.2)	0.10	0.71
MCS (0–100)	50.9 (10.7)	52.8 (9.6)	48.1 (11.7)	0.44	0.10

Notes: Differences between men and women in the sample were examined by t-tests, chi-square tests, and Fisher’s exact test. ESs are Cohen’s d. Higher scores on PCS and MCS reflect higher HRQoL.

Abbreviations: ES, effect size; HRQoL, health-related quality of life; M, mean; MCS, quality of life mental component score; PCS, quality of life physical component score; SD, standard deviation.

Table 3 Bivariate associations between the study variables in the sample at baseline (N=60)

Variable	PCS		MCS
	r	P	r	P
Age	−0.10	0.43	0.17	0.20
Sex	−0.05	0.71	−0.22	0.10
Education	0.01	0.94	0.00	0.99
Relationship status	−0.17	0.20	0.14	0.31
Work status	−0.31	0.02	0.02	0.89
Social support	−0.02	0.90	0.30	0.02
Physical activity	0.05	0.72	−0.04	0.75
Consequences	−0.57	<0.001	−0.14	0.29
Timeline	−0.25	0.05	0.25	0.06
Personal control	0.07	0.58	−0.05	0.71
Treatment control	0.04	0.76	−0.28	0.03
Identity	−0.66	<0.001	0.04	0.77
Concern	−0.33	0.01	−0.27	0.04
Understanding	−0.17	0.18	0.15	0.25
Emotional response	−0.24	0.07	−0.44	<0.001
Self-efficacy	0.12	0.35	0.26	0.04
PCS			−0.13	0.33

Notes: Table content is Pearson’s correlation coefficient (r) and corresponding P-values. Coding: male =1, female =2; education of 12 years or less =1, more than 12 years of education =2; living in paired relationship =1, not living in paired relationship =0; in paid work =0, not in paid work =1. Higher scores on PCS and MCS reflect higher HRQoL. All other measures are continuous measures, for which higher scores indicate higher levels.

Abbreviations: PCS, quality of life physical component score; MCS, quality of life mental component score.

Table 4 Predictors of health-related quality of life at baseline and at one-year follow-up by hierarchical regression analysis (N=60)

Variable	Baseline PCS			One-year PCS
	r	B1	B2	r	B1	B2
Consequences	−0.57a	−0.30a	−0.35a	−0.56a	−0.38a	−0.41a
Identity	−0.66a	−0.49a	−0.47a	−0.53a	−0.32b	−0.31b
Explained varianced		49.1%			38.1%
Self-efficacy	0.12		−0.17	0.04		−0.09
R^2 changec			2.7%			0.7%
Explained varianced			51.8%			38.7%
Variable	Baseline MCS			One-year MCS
	r	B1	B2	r	B1	B2
Timeline	0.25	0.21	0.20	0.06	0.08	0.07
Treatment control	−0.28b	−0.19	−0.17	0.09	0.15	0.16
Emotional response	−0.44a	−0.42a	−0.35a	−0.31b	−0.33b	−0.30b
Explained varianced		28.9%			11.8%
Self-efficacy	0.26b		0.18	0.12		0.07
Social support	0.30b		0.25b	0.19		0.17
R^2 changec			9.2%			3.1%
Explained varianced			38.1%			14.9%

Notes: Higher scores on PCS and MCS reflect higher HRQoL. At both time points, illness perception variables were entered as independent variables in the first block (B1), whereas self-efficacy (for PCS) and self-efficacy and social support (for MCS) were entered as additional independent variables in the second block (B2). Table content is bivariate correlation coefficients (Pearson’s r) and standardized beta coefficients (β).

a P<0.01

b P<0.05

c R² change is the amount of variance in the dependent variable accounted for by the second block of independent variables

d explained variance is the total amount of variance explained by the models.

Abbreviations: HRQoL, health-related quality of life; MCS, quality of life mental component score; PCS, quality of life physical component score.