Socioeconomic status and COPD among low- and middle-income countries

Figures & data

Table 1 Sociodemographic characteristics and COPD prevalence stratified by site

Variables	Bariloche	Canelones	Dhaka	Lima	Marcos Paz	Matlab	Rural Puno	Temuco	Tumbes	Urban Puno
COPD positive, n (%)	82 (7)	96 (10)	182 (10)	56 (6)	175 (14)	284 (15)	43 (9)	52 (5)	16 (2)	25 (5)
SES composite index, mean (SD)	0.60 (1.34)	−0.63 (1.37)	1.02 (1.48)	−0.09 (1.06)	−0.09 (1.15)	−0.55 (1.44)	−1.67 (0.82)	0.81 (1.89)	−0.73 (0.93)	−0.04 (1.27)
SES composite index, interquartile difference (25^th and 75^th percentile)	2.08 (−0.53, 1.55)	1.09 (−1.93, −0.85)	2.90 (0.50, 2.95)	1.09 (−0.94, 0.14)	1.09 (−1.03, 0.06)	1.99 (−1.59, 0.51)	1.09 (−2.03, −0.95)	3.98 (−0.40, 3.59)	1.09 (−1.04, 0.05)	1.99 (−1.40, 0.59)
Age in years, median (IQR)	56.7 (50.5, 63.0)	59.2 (52.1, 66.2)	50.0 (43.5, 56.5)	54.7 (45.6, 63.7)	58.4 (51.6, 65.3)	53.0 (45.0, 61.0)	54.9 (45.6, 64.3)	58.8 (51.6, 66.0)	54.8 (44.9, 64.6)	54.7 (44.9, 64.4)
Number of males (%)	431 (39)	375 (40)	853 (45)	491 (49)	498 (40)	848 (51)	239 (47)	484 (46)	480 (50)	250 (49)
Height in m, median (IQR)	1.61 (1.54, 1.68)	1.62 (1.55, 1.68)	1.55 (1.48, 1.62)	1.54 (1.48, 1.60)	1.61 (1.54, 1.68)	1.53 (1.47, 1.60)	1.55 (1.49, 1.61)	1.60 (1.53, 1.67)	1.58 (1.52, 1.65)	1.57 (1.50, 1.64)
BMI in kg/m^2, mean (SD)	28.9 (5.6)	29.6 (6.2)	24.5 (4.8)	28.4 (4.5)	30.1 (5.8)	20.6 (3.6)	25.2 (3.7)	29.1 (4.9)	28.4 (4.8)	27.9 (4.4)
BMI ≥30 kg/m^2, n (%)	417 (38)	398 (42)	234 (13)	324 (33)	577 (47)	29 (2)	54 (10.7)	389 (37)	306 (32)	136 (27)
Daily smokers, n (%)	263 (24)	205 (22)	119 (6)	32 (3)	284 (23)	165 (9)	1 (0)	161 (15)	53 (6)	11 (2)
Pack-years of smoking, mean (SD)	19.7 (7.9, 31.4)	27.7 (12.8, 42.6)	15.6 (4.5, 26.7)	0.2 (0.0, 1.0)	28.7 (16.8, 40.6)	15.6 (5.9, 25.4)	0.1 (0.0, 0.3)	8.5 (1.9, 15.2)	0.6 (0.0, 2.9)	0.1 (0.0, 0.8)
Biomass as primary source of fuel, n (%)	254 (23)	43 (5)	66 (4)	24 (3)	6 (1)	1,805 (98)	481 (95)	233 (22)	163 (17)	10 (2)
Household size, median (IQR)	9 (8, 10)	9 (8, 10)	5 (4, 6)	5 (3.5, 6.5)	9 (7.5, 10.5)	5 (3.5, 6.5)	3 (1.5, 4.5)	9 (7.5, 10.5)	4 (3, 5)	4 (3, 5)
Education ≥ secondary, n (%)	548 (50)	469 (50)	815 (64)	456 (46)	426 (34)	346 (19)	169 (34)	752 (71)	347 (36)	329 (65)
Monthly household income categories, n (%)
Lowest	24 (3)	86 (10)	89 (5)	2 (0)	15 (3)	360 (20)	148 (40)	68 (9)	11 (1)	8 (2)
Second	86 (9)	368 (41)	91 (5)	179 (19)	101 (18)	384 (21)	176 (47)	123 (17)	439 (47)	110 (26)
Third	237 (25)	292 (32)	315 (17)	432 (46)	224 (40)	541 (29)	41 (11)	115 (16)	354 (38)	136 (31)
Fourth	239 (25)	43 (5)	374 (20)	200 (21)	126 (23)	273 (15)	7 (2)	45 (6)	83 (9)	96 (22)
Fifth	184 (20)	12 (1)	359 (19)	83 (9)	66 (12)	174 (9)	0 (0)	22 (3)	30 (3)	45 (10)
Highest	170 (18)	101 (11)	646 (34)	52 (5)	28 (5)	114 (6)	3 (1)	357 (49)	20 (2)	37 (9)

Abbreviations: SES, socioeconomic status; IQR, interquartile range; BMI, body mass index.

Figure 1 Prevalence of COPD per city using the lower limit of normal (LLN) method of diagnosis with Global Lung Function Initiative (GLI) mixed ethnic population, presented as overall and stratified by sex.

Figure 2 Pre-bronchodilator FEV₁/FVC Z-score using Global Lung Function Initiative (GLI) mixed ethnic population, stratified by age and sex.

Notes: Age is stratified into four categories. Males are represented by red box plots and females by green, in ten panels each representing an individual site.

Figure 3 Mean pre-bronchodilator FEV₁ and FEV₁/FVC Z-score using Global Lung Function Initiative (GLI) mixed ethnic population, by elevation in meters and site.

Notes: Elevation is in meters on the x-axis with Z-score on the y-axis. City names are beside each corresponding point. The lines represent the fitted values of a regression line of Z-score by elevation.

Table 2 Unadjusted and adjusted alternating logistic regression models for COPD using the lower limit of normal (LLN) method of diagnosis with Global Lung Function Initiative (GLI) mixed ethnic population, coefficients reported as odds ratios

Variables	Unadjusted		Adjusted model (individual SES indicators)		Adjusted models (SES composite index)
	OR (95% CI)	P-value	OR (95% CI)	P-value	OR (95% CI)	P-value
Monthly household income (change per category)	0.93 (0.87, 1.00)	0.04	0.96 (0.93, 0.99)	0.01
Median household size (household size <4 as reference)	1.10 (0.93, 1.32)	0.26	1.08 (0.90, 1.30)	0.42
Secondary school or higher (below secondary as reference)	0.71 (0.51, 0.98)	0.04	0.73 (0.55, 0.98)	0.04
Composite SES index (interquartile difference)	1.23 (1.01, 1.50)	0.04			1.23 (1.05, 1.43)	0.01
Age (per decade increase)	1.48 (1.35, 1.62)	<0.001	1.41 (1.31, 1.51)	<0.001	1.43 (1.33, 1.55)	<0.001
Female (male as reference)	0.46 (0.29, 0.72)	<0.001	0.51 (0.34, 0.78)	<0.001	0.54 (0.36, 0.80)	0.002
Daily smokers (nondaily and nonsmokers as reference)	2.66 (2.10, 3.37)	<0.001	2.25 (1.74, 2.92)	<0.001	2.25 (1.76, 2.89)	<0.001
Biomass as primary source of fuel	1.73 (1.44, 2.09)	<0.001	1.52 (1.23, 1.89)	<0.001	1.59 (1.31, 1.94)	<0.001

Abbreviations: SES, socioeconomic status; OR, odds ratio.

Figure 4 Odds ratio of COPD by socioeconomic status composite index (SES index), secondary education or higher (below secondary as reference), greater than or equal to median household size of 4 (below as reference), and monthly household income (change per category).

Notes: Adjusted odds ratios are displayed for the overall sample (left) and for individual sites (right). In the left panel, the square represents the adjusted odds ratio and the segments represent 95% CIs. In the right panel, the triangles represent site-specific adjusted odds ratios. For the composite SES index, we calculate the interquartile odds ratio of COPD, ie, the ratio of odds of COPD between the 25^th vs 75^th percentile of the composite SES index.
Abbreviation: SES, socioeconomic status.

Table 3 Unadjusted and adjusted random effects linear regression models for pre-bronchodilator FEV₁/FVC Z-score using Global Lung Function Initiative (GLI) mixed ethnic population

Variables	Unadjusted		Adjusted model (individual SES indicators)		Adjusted models (SES composite index)
	Difference (95% CI)	P-value	Difference (95% CI)	P-value	Difference (95% CI)	P-value
Monthly household income (change per category)	0.05 (0.03, 0.07)	<0.001	0.04 (0.02, 0.06)	<0.001
Median household size (household size <4 as reference)	0.04 (−0.01, 0.09)	0.13	0.03 (−0.03, 0.08)	0.32
Secondary school or higher (below secondary as reference)b	0.12 (0.17, 0.77)	<0.001	0.10 (0.05, 0.15)	<0.001
Composite SES index (interquartile difference)	−0.15 (−0.16, −0.13)	<0.001			−0.14 (−0.09, −0.19)	<0.001
Age (per decade increase)	−0.08 (−0.11, −0.06)	<0.001	−0.07 (−0.09, −0.05)	<0.001	−0.08 (−0.10, −0.06)	<0.001
Female (male as reference)	0.19 (0.14, 0.23)	<0.001	0.18 (0.13, 0.23)	<0.001	0.17 (0.12, 0.21)	<0.001
Daily smokers (nondaily and nonsmokers as reference)	−0.40 (−0.47, −0.33)	<0.001	−0.41 (−0.49, −0.33)	<0.001	−0.40 (−0.48, −0.33)	<0.001
Biomass as primary source of fuel	−0.22 (−0.30, −0.13)	<0.001	−0.17 (−0.26, −0.08)	<0.001	−0.18 (−0.27, −0.09)	<0.001

Abbreviation: SES, socioeconomic status.

Figure 5 Absolute difference in pre-bronchodilator FEV₁/FVC Z-score by socioeconomic status composite index (SES index), secondary education or higher (below secondary as reference), greater than or equal to household size of 4 (below as reference), and monthly household income (change per category).

Notes: We display adjusted differences in pre-bronchodilator FEV₁/FVC Z-score for the overall sample (left) and for individual sites (right). In the left panel, the square represents the adjusted odds ratio and the segments represent 95% CIs. In the right panel, the triangles represent site-specific adjusted odds ratios. For the composite SES index, we calculate the interquartile adjusted difference in pre-bronchodilator FEV₁/FVC Z-score, ie, the difference between the 75th and 25th percentiles of the composite SES index.
Abbreviation: SES, socioeconomic status.