The Association Between Neighborhood Socioeconomic Disadvantage and Chronic Obstructive Pulmonary Disease

Figures & data

Table 1 Patient Characteristics by ADI Quintile

Participant Characteristics	All Patients	ADI National Ranking by Quintile					P-value
		Q1	Q2	Q3	Q4	Q5
		N=375	N=349	N=366	N=360	N=349
Age (y)	65.15 ± 8.07	68.39 ± 7.18	66.13 ± 7.54	64.33 ± 7.87	63.92 ± 8.22	62.82 ± 8.33	<0.001
Female (%)	766 (42.6%)	154 (41.1%)	123 (35.2%)	151 (41.3%)	169 (46.9%)	169 (48.4%)	0.003
White/Caucasian (%)	1458 (81.0%)	332 (88.5%)	296 (84.8%)	315 (86.1%)	302 (83.9%)	213 (61.0%)	<0.001
More than high school (%)	1096 (61.1%)	295 (79.3%)	227 (65.2%)	222 (60.7%)	194 (53.9%)	158 (45.3%)	<0.001
Income							<0.001
≤ $49,999	913 (51.2%)	126 (34.1%)	142 (41.0%)	196 (53.8%)	212 (59.4%)	237 (68.5%)
≥$50,000	552 (31.0%)	170 (45.9%)	145 (41.9%)	108 (29.7%)	88 (24.6%)	41 (11.8%)
Declined to Answer	318 (17.8%)	74 (20.0%)	59 (17.1%)	60 (16.5%)	57 (16.0%)	68 (19.7%)
Married (%)	886 (49.3%)	189 (50.7%)	203 (58.2%)	181 (49.6%)	183 (50.8%)	130 (37.2%)	<0.001
Lives in urban areas (%)^a	1579 (87.8%)	360 (96.0%)	318 (91.1%)	311 (85.0%)	279 (77.5%)	311 (89.1%)	<0.001
Body mass index	27.37 ± 5.32	27.25 ± 4.99	27.25 ± 5.18	27.62 ± 5.03	27.36 ± 5.72	27.38 ± 5.66	0.877
Current smoker (%)	607 (34.3%)	82 (22.2%)	91 (26.6%)	156 (43.6%)	123 (34.6%)	155 (44.9%)	<0.001
Pack years	52.75 ± 27.66	53.12 ± 26.48	53.16 ± 23.70	51.53 ± 22.74	52.68 ± 33.07	53.32 ± 31.03	0.910
Occupational Exposure (%)^b							<0.001
No	882 (49.6%)	225 (60.5%)	166 (48.0%)	172 (47.8%)	161 (45.0%)	158 (45.9%)
Yes	725 (40.7%)	106 (28.5%)	139 (40.2%)	153 (42.5%)	170 (47.5%)	157 (45.6%)
Do not Know	173 (9.7%)	41 (11.0%)	41 (11.8%)	35 (9.7%)	27 (7.5%)	29 (8.4%)
Lung Function
FEV1% predicted	60.96 ± 23.06	67.50 ± 25.15	61.21 ± 24.18	60.15 ± 21.24	57.66 ± 22.11	57.96 ± 20.93	<0.001
COPD-Related Variables
Quality of Life and Respiratory Symptoms
CAT	15.44 ± 7.99	12.38 ± 7.21	14.52 ± 7.24	15.79 ± 8.08	16.47 ± 8.03	18.39 ± 8.13	<0.001
SGRQ	37.93 ± 19.80	30.38 ± 17.72	36.18 ± 19.59	37.75 ± 19.77	41.11 ± 20.10	44.72 ± 18.89	<0.001
MRC	1.26 ± 1.04	1.10 ± 0.99	1.20 ± 1.03	1.26 ± 1.03	1.35 ± 1.07	1.41 ± 1.04	0.001
6-minute walk distance (m)	392.88 ± 128.14	409.24 ± 113.15	406.12 ± 121.14	393.14 ± 135.92	373.90 ± 126.92	381.61 ± 139.48	0.001
Ease of cough and sputum	9.62 ± 3.47	8.47 ± 2.93	9.41 ± 3.32	9.76 ± 3.54	9.84 ± 3.41	10.67 ± 3.76	<0.001
CT Imaging
Airway wall thickness	3.72 ± 0.08	3.71 ± 0.08	3.73 ± 0.08	3.73 ± 0.09	3.71 ± 0.08	3.72 ± 0.09	0.001
Percentage emphysema	11.21 ± 11.32	10.84 ± 10.66	12.73 ± 12.12	10.63 ± 11.24	11.55 ± 11.29	10.34 ± 11.20	0.041
Percentage gas trapping	33.76 ± 20.91	33.47 ± 20.63	35.89 ± 21.03	32.64 ± 20.14	34.37 ± 21.44	32.48 ± 21.29	0.180
Rate of Exacerbations
Any (count/year)^c	0.60 ± 1.00	0.36 ± 0.67	0.54 ± 0.87	0.65 ± 1.14	0.69 ± 1.08	0.77 ± 1.14	<0.001
Severe (count/year)^c	0.21 ± 0.59	0.11 ± 0.34	0.12 ± 0.30	0.23 ± 0.72	0.21 ± 0.55	0.36 ± 0.82	<0.001
Psychosocial Wellbeing
Depressive symptom score	4.69 ± 3.52	3.90 ± 3.04	4.27 ± 3.39	4.51 ± 3.58	5.48 ± 3.81	5.37 ± 3.49	<0.001
Anxiety symptom score	5.62 ± 3.78	4.89 ± 3.52	5.27 ± 3.71	5.67 ± 3.67	6.10 ± 3.90	6.21 ± 3.94	<0.001
Area Deprivation Index
ADI (National Ranking)	41.00 ± 29.40	5.18 ± 3.25	19.84 ± 5.01	37.75 ± 5.54	57.40 ± 6.35	87.14 ± 10.00

Notes: ^aUrban areas are non-rural areas as classified by US Census 2010. The definition is based on US Census classification of rural versus non-rural. ^bThose who answered “Don’t know” (n=173) were counted as ever exposed. ^cRate of exacerbation defined as the total number of oral antibiotics or steroid use due to worsening respiratory symptoms divided by the total number of days in the study and multiplied by 365. Rate of severe exacerbation defined as the total number of hospitalization due to worsening respiratory symptoms divided by the total number of days in the study and multiplied by 365.

Abbreviations: CAT, COPD assessment test; SGQR, St. George’s Respiratory Questionnaire; MRC, Medical Research Council Dyspnea Score.

Figure 1 Distribution of ADI national rank by covariate levels. For continuous covariates (age, BMI, FEV1% predicted, pack years), the variables were dichotomized in the way it is described in the legends.

Table 2 Regression of COPD-Related Outcomes on Quintile ADI

COPD-Related Outcome	Unadjusted			Adjusted
	Predicted Difference (95% CI) Between Quintile 5 vs. Quintile 1	p-value	p-value for the Linear Trend of Quintiles	Predicted Difference (95% CI) Between Quintile 5 vs. Quintile 1	p-value	p-value for the Linear Trend of Quintiles
Quality of Life/Respiratory Symptoms
CAT	4.29	<0.001	<0.001	1.59	<0.001	0.002
	(2.54, 6.04)			(0.74, 2.44)
SGRQ	10.10	<0.001	<0.001	3.13	0.006	0.016
	(5.08, 15.13)			(0.88, 5.37)
MRC	0.19	0.004	0.004	−0.05	0.416	0.556
	(0.06, 0.32)			(−0.16, 0.07)
6-minute walk distance (meters)	−45.12	<0.001	<0.001	−24.69	0.003	0.002
	(−61.02, −29.21)			(−41.05, −8.32)
Ease of cough and sputum	2.06	<0.001	<0.001	1.12	<0.001	<0.001
	(1.63, 2.49)			(0.62, 1.63)
Chest CT Imaging
Airway thickness (x10^−2)	2.24	<0.001	<0.001	1.25	0.003	0.017
	(1.64, 2.85)			(0.44, 2.06)
Percent emphysema	−2.10	0.043	0.077	−1.11	0.178	0.089
	(−4.14, −0.07)			(−2.73, 0.51)
Percent gas trapping	−2.96	0.093	0.159	−1.14	0.210	0.227
	(−6.41, 0.49)			(−2.92, 0.64)
Rate of Exacerbations
Any exacerbations (IRR)^a	1.63	<0.001	0.001	1.56	<0.001	<0.001
	(1.25,2.14)			(1.32,1.84)
Severe exacerbations (IRR)^a	2.76	<0.001	<0.001	2.02	<0.001	<0.001
	(1.65,4.61)			(1.36,2.98)
Psychosocial Wellbeing
Depressive symptom score	0.95	0.025	0.004	−0.05	0.887	0.477
	(0.12, 1.78)			(−0.70, 0.60)
Anxiety symptom score	1.06	<0.001	<0.001	0.13	0.495	0.264
	(0.52, 1.59)			(−0.25, 0.52)

Notes: In all analyses, generalized linear mixed model with robust standard error estimator was used. For continuous outcomes (quality of life/respiratory symptoms and chest CT imaging), Gaussian family distribution and identity link function were employed; and, the predicted difference represented the difference in the level of the outcome between the highest and the lowest quintile ADI. For count outcomes (exacerbations), negative binomial family distribution and log link function were employed, along with adjustment for the number of days in the study as an offset; and, the predicted difference represented the incidence rate ratio for the highest quintile ADI in comparison to the lowest quintile ADI. Adjusted model adjusted for age, sex, race, education, income, marital status, rural status, BMI, FEV1% Predicted, smoking status, pack years, and occupational exposure. ^aFor regression analysis, airway thickness was rescaled by a factor of 100 in order that the effect estimates would represent the estimates at the hundredth level.

Figure 2 Average predicted difference between top and bottom quantile ADI national rank: the most-disadvantaged vs the least-disadvantaged neighborhoods. *Six-minute walk was rescaled by a factor of one-tenth (e.g., the value −2 meters indicates −20 meters). ^#For exacerbation variables only, Y-axis indicates the rate ratio (e.g., the value of 2 would indicate the rate of exacerbation that is twice as great for the most disadvantaged neighborhood than that for the least disadvantaged).

Notes: Y-axis represents the regression coefficient for the most-disadvantaged 20th percentile (with the least-disadvantaged 20th percentile as the reference category) in the fully adjusted regression of outcomes on quintile ADI.

Table 3 Regression of COPD-Related Outcomes on Continuous ADI

COPD-Related Outcome	Unadjusted		Adjusted
	Predicted Difference (95% CI)	p-value	Predicted Difference (95% CI)	p-value
Quality of Life/Respiratory Symptoms
CAT	1.46	<0.001	0.57	<0.001
	(0.87, 2.04)		(0.25, 0.88)
SGRQ	3.36	<0.001	0.94	0.034
	(1.63, 5.08)		(0.07, 1.81)
MRC	0.07	0.006	−0.01	0.722
	(0.02, 0.13)		(−0.06, 0.04)
6-minute walk distance (meters)	−18.21	<0.001	−11.04	<0.001
	(−25.59, −10.84)		(−16.98, −5.10)
Ease of cough and sputum	0.63	<0.001	0.35	<0.001
	(0.47, 0.78)		(0.18, 0.52)
Chest CT Imaging
Airway thickness (x10^−2)	0.63	<0.001	0.33	0.029
	(0.37, 0.89)		(0.03, 0.63)
Percent emphysema	−0.85	0.080	−0.56	0.066
	(−1.81, 0.10)		(−1.16, 0.04)
Percent gas trapping	−1.12	0.165	−0.57	0.119
	(−2.69, 0.46)		(−1.29, 0.15)
Rate of Exacerbations
Any exacerbations (IRR)^a	1.17	0.005	1.15	0.002
	(1.05,1.31)		(1.05,1.25)
Severe exacerbations (IRR)^a	1.44	<0.001	1.28	<0.001
	(1.24,1.67)		(1.15,1.42)
Psychosocial Wellbeing
Depressive symptom score	0.44	0.005	0.10	0.386
	(0.13, 0.75)		(−0.12, 0.31)
Anxiety symptom score	0.38	<0.001	0.04	0.543
	(0.23, 0.54)		(−0.09, 0.17)

Notes: In all analyses, generalized linear mixed model with robust standard error estimator was used. For continuous outcomes (quality of life/respiratory symptoms and chest CT imaging), Gaussian family distribution and identity link function were employed; and, the predicted difference represented the difference in the level of the outcome for one standard deviation increase in ADI national rank. For count outcomes (exacerbations), negative binomial family distribution and log link function were employed, along with adjustment for the number of days in the study as an offset; and, the predicted difference represented the incidence rate ratio for the one standard deviation increase in ADI national rank. Adjusted model adjusted for age, sex, race, education, income, marital status, rural status, BMI, FEV1% Predicted, smoking status, pack years, and occupational exposure. ^aFor regression analysis, airway thickness was rescaled by a factor of 100 in order that the effect estimates would represent the estimates at the hundredth level.

Figure 3 Association of continuous ADI and COPD-related outcomes by rural status. The charts illustrate the interactions between continuous ADI and rural status on their associations with SGRQ, dyspnea, and 6-minute walk distance. The y-axis represents the predicted difference in outcome for one SD increase in ADI based on the fully adjusted regression model adjusting for age, sex, education, income, marital status, BMI, FEV1% predicted, smoking status, pack years, and occupational exposure.