Chronic Obstructive Pulmonary Disease Illness and Medication Beliefs are Associated with Medication Adherence

Figures & data

Table 1.   Characteristics of COPD patients by Self-Reported Medication Adherence

Characteristic	Total n = 188	Adherent N = 79	Non-Adherent n = 109	p-value
Age, years, median (IQR)	67 (62–74)	71 (67–76)	64 (61–71)	<0.0001
Male, no. (%)	62 (33)	26 (33)	36 (33)	0.99
Race, no. (%)
White	69 (37)	42 (53)	27 (25)	0.001
Black	89 (47)	29 (37)	60 (55)
Hispanic	26 (13)	7 (9)	19 (17)
Other	4 (2)	1 (1)	3 (3)
Income, monthly < $1350, no. (%)	90 (48)	30 (38)	60 (55)	0.02
Education, no. (%)
Some high school or less	45 (24)	10 (13)	35 (32)	0.002
High school graduate	37 (20)	19 (24)	18 (17)
Some college	50 (27)	18 (23)	32 (30)
College graduate or more years	55 (29)	32 (40)	23 (21)
Limited English proficiency, no. (%)	15 (8)	4 (5)	11 (10)	0.21
COPD Severity Scale score, median (IQR)	5 (3–8)	5 (2–8)	6 (4–9)	0.04
≥1 ED visit for COPD in past year, no. (%)	47 (25)	18 (23)	29 (27)	0.56
Ever intubated for COPD, no. (%)	11 (6)	6 (8)	5 (5)	0.39

COPD: chronic obstructive pulmonary disease; ED: emergency department.

Table 2.   Unadjusted comparisons of beliefs according to self-reported adherence

Illness and Medication Beliefs	Adherent Mean (SD)	Non-Adherent Mean (SD)	Effect Size	p-value
Brief Illness Perceptions Questionnaire^1
CSM^2 Domain: Identity
How much do you experience symptoms from your COPD?	6.1 (2.9)	6.4 (2.7)	0.14	0.46
CSM Domain: Timeline
How long do you think your COPD will continue?	9.1 (2.1)	8.9 (2.5)	0.09	0.79
CSM Domain: Control
How much control do you feel you have over your COPD?	6.8 (2.5)	6.6 (2.5)	0.04	0.76
How much do you think your treatment can help your COPD?	7.9 (2.2)	7.7 (2.4)	0.11	0.60
CSM Domain: Consequences
How much does your COPD affect your life?	5.8 (3.0)	6.4 (2.7)	0.23	0.15
Emotional Representations
How concerned are you about your COPD?	7.6 (3.4)	8.8 (2.2)	0.43	0.01
How much does your COPD affect you emotionally?	4.8 (3.6)	6.6 (3.3)	0.54	0.001
Comprehensibility
How well do you understand your COPD	8.5 (2.2)	8.2 (2.4)	0.15	0.29
Beliefs about Medications Questionnaire
Medication Necessity Score^2	14.4 (4.0)	14.1 (4.7)	0.07	0.54
Concerns About Medications Score^3	11.4 (3.2)	14.4 (4.1)	0.81	<0.0001

¹Each item scored on scale of 0–10; higher scores indicate greater disease congruence.

²Possible score range 5–25; higher score indicates greater belief that COPD medications are necessary.

³Possible score range 5–25; higher score indicates greater worry about COPD medications.

CSM: Common Sense Model of Self-Regulation.

Table 3.   Adjusted association between COPD illness and medication beliefs and medication adherence

Illness and Medication Beliefs	Odds Ratio^1	95% Confidence Interval
Brief Illness Perceptions Questionnaire^2
CSM Domain: Identity
How much do you experience symptoms from your COPD?	1.23	0.77–1.99
CSM Domain: Timeline
How long do you think your COPD will continue?	0.94	0.57–1.56
CSM Domain: Control
How much control do you feel you have over your COPD?	0.95	0.61–1.48
How much do you think your treatment can help your COPD?	1.29	0.80–2.09
CSM Domain: Consequences
How much does your COPD affect your life?	1.03	0.67–1.59
Emotional Representations
How concerned are you about your COPD?	0.79	0.52–1.20
How much does your COPD affect you emotionally?	0.68	0.48–0.96
Comprehensibility
How well do you understand your COPD	1.20	0.76–1.92
Beliefs about Medications Questionnaire
Medication Necessity Score^3	0.95	0.76–1.20
Concerns About Medications Score^4	0.49	0.35–0.70

¹Adjusted for age, sex, race, education, COPD severity and beliefs.

²Higher scores indicate greater disease congruence of a belief.

³Higher score indicates greater belief that COPD medications are necessary.

⁴Higher score indicates greater worry about COPD medications.

CSM: Common Sense Model of Self-Regulation.