Potential Explanatory Factors for the Concurrent Experience of Dyspnea and Pain in Patients with COPD

Figures & data

Table 1. Demographic characteristics and outcome measures of participants.

Characteristic	%/mean (SD)
N	301
Age in years	67.5 (8.4)
Male	80.7%
Education:
Did not graduate from high school	6.6%
High school graduate	15.9%
Some college or vocational school	51.8%
College graduate	25.9%
Race/Ethnicity^a
African American	7.6%
Asian	1.0%
Hawaiian or Pacific Islander	0.3%
Native American or Alaskan Native	4.6%
Caucasian	87.3%
Hispanic/Latino	2.0%
Other	1.3%
Married or partnered	56.5%
Smoked in prior week	28.5%
Comorbidities^b
None	46.1%
One	31.8%
Two or more	22.2%
Body Mass Index (BMI)
<18.5	3.0%
18.5–24.9	28.9%
25–29.9	35.2%
>30	32.8%
Sleep apnea (by STOP-BANG score > = 4)	27.9%
PHQ-9 depression severity (out of 27 points)
Minimal (0–4)	44.9%
Mild (5–9)	33.9%
Moderate (10–14)	14.6%
Severe (> =15)	7.0%
Hospital Anxiety and Depression Scale - Anxiety (out of 21 points)
Minimal (0–7)	75.0%
Mild (8–10)	15.3%
Moderate (11–14)	10.0%
% predicted FEV1 pre-bronchodilator	41.6 (15.2)
% predicted FEV1 post-bronchodilator	45.7 (16.5)
FEV1/FVC pre-bronchodilator	0.45 (0.13)
FEV1/FVC post-bronchodilator	0.45 (0.12)
Mean hand grip strength (kg)	32.3 (9.5)
Six-minute walk distance (in feet or meters)	1085 (371) ft or 330.7 (113.1) m
GOLD COPD Severity Category
A	20.2%
B	12.9%
C	22.5%
D	44.5%
UCSD Dyspnea scale (normed to 100 points)	42.7 (23.0)
UCSD Dyspnea scale categories (normed to 100 points)
0–19	18.2%
20–39	30.2%
40–59	28.8%
60–79	14.2%
80–100	8.6%
Mean SF-36 pain severity score (normed to 100 points)^c	38.3 (24.2)
SF-36 pain severity score categories (normed to 100 points)^c
0–19	27.2%
20–39	27.5%
40–59	28.5%
60–79	15.2%
80–100	1.6%

^aThe total is greater than 100% because participants could answer positive to multiple categories.

^bNon-COPD comorbidities included in the Charlson Score.

^cSF-bodily pain and SF-pain interference scores were converted to a 100-point scale, averaged, and reverse coded so that higher scores indicate more pain.

Figure 1. Cross-sectional associations between pain and dyspnea.

Figure 2. Longitudinal associations between pain and dyspnea.

Table 2. Regression models for dyspnea as a predictor of pain.

Predictor of pain	Model 1: Unadjusted model	Model 2: Adjusted for demographics^a, BMI, GOLD category, and comorbidity	Model 3: Adjusted for demographics^a, BMI, GOLD category, comorbidity, and other predictors^b	Model 4: Adjusted for demographics^a, BMI, GOLD category, comorbidity, other predictors^b, and biomarkers^c
Dyspnea – cross-sectional	0.78 (0.73–0.82) p < 0.001	0.79 (0.74–0.84) p < 0.001	0.57 (0.49–0.65) p < 0.001	0.77 (0.72–0.82) p < 0.001
Dyspnea – coincident yearly change	0.41 (0.33–0.48) p < 0.001	0.41 (0.28–0.53) p < 0.001	0.36 (0.23–0.50) p < 0.001	0.42 (0.28–0.56) p < 0.001

^aAge, sex, race, marital status, education.

^bDepression, anxiety, predicted FEV1, sleep apnea, hand grip strength, walking distance.

^cIL1, IL2, IL4, IL5, IL6, IL7, IL8, IL10, IL12, IL3, interferon, GMCSF, TNF, CRP; none were significant predictors of pain at p < 0.01.

Table 3. Significant predictors of pain in regression models that include dyspnea.

	Predictor of pain	Model 1: Unadjusted, in models only including dyspnea	Model 2: Adjusted for dyspnea, demographics^a	Model 3: Adjusted for dyspnea, demographics^a, and other predictors^b	Model 4: Adjusted for dyspnea, demographics^a, and biomarkers^c
Cross-sectional	Pre-bronchodilator FEV1 (per 10 percentage points worse)	5.36 (4.34–6.39) p < 0.001	1.64 (0.84–2.45) p < 0.001	0.39 (−0.60 to 1.47) p = 0.475	0.13 (−0.60 to 0.90) p = 0.741
	Depression (0-27 scale, per point worse)	1.47 (1.05–1.89) p < 0.001	0.48 (0.19–0.79) p = 0.001	0.68 (0.15–0.89) p = 0.012	0.36 (0.06–0.66) p = 0.018
	Anxiety (0-21 scale, per point worse)	0.78 (0.34–1.21) p < 0.001	0.07 (−0.38 to 0.24) p = 0.656	0.12 (−0.41 to 0.64) p = 0.321	0.16 (−0.56 to 0.22) p = 0.404
	6-minute walk distance (per 100 fewer feet or 30.5 meters walked)	1.44 (1.14–1.74) p < 0.001	1.45 (1.13–1.77) p < 0.001	1.40 (1.00–1.94) p < 0.001	1.36 (1.05–1.68) p < 0.001
Coincident yearly change	FEV1 (% predicted) change, per 10 percentage point worsening	0.97 (0.36–1.57) p = 0.002	0.92 (0.31–1.54) p = 0.003	0.23 (−0.73 to 1.24) p = 0.636	0.17 (0.052–0.755) p = 0.718
	Depression (0-21 scale, per point worse)	0.48 (0.14–0.83) p = 0.006	0.50 (0.14–0.86) p = 0.007	0.47 (−0.36 to 1.32) p = 0.260	0.05 (−0.77 to 0.88) p = 0.127
	BMI change (per BMI point increase)	1.31 (0.55–2.06) p = 0.001	0.90 (−0.28 to 2.08) p = 0.131	2.33 (0.73–3.93) p = 0.005	2.38 (0.68–4.09) p = 0.007

^aAge, sex, race, marital status, education, BMI, GOLD category, comorbidities.

^bDepression, anxiety, predicted FEV1, sleep apnea, hand grip strength, walking distance. The baseline values were used for cross-sectional models, and the year-to-year change was used in the longitudinal models.

^cIL1, IL2, IL4, IL5, IL6, IL7, IL8, IL10, IL12, IL3, interferon, GMCSF, TNF, CRP; none were significant predictors of pain at p < 0.01.

Data availability statement

Due to the nature of this research, participants of this study did not agree for their data to be shared publicly, so supporting data are not available.