Associations between occupational inhalation risks and FeNO levels in airway obstruction patients: results from the National Health and Nutrition Examination Survey, 2007–2012

Figures & data

Figure 1 Flow diagram of selection process.

Abbreviations: MEC, Mobile Examination Center; NHANES, National Health and Nutrition Examination Survey.

Table 1 Demographic characteristics and occupational exposure of subjects with and without COPD

Demographics	With COPD (n=1,766)	Without COPD (n=11,570)	P-value
Age (years)	56.12 (0.49)	43.17 (0.34)	<0.001*
Smoking (pack-years)	18.78 (0.95)	5.28 (0.27)	<0.001*
Gender, n (%)			<0.001*
Male	1,129 (61.1%)	5,526 (47.6%)
Female	637 (38.9%)	6,044 (52.4%)
Race, n (%)			<0.001*
Mexican American	131 (2.7%)	1,979 (9.3%)
Other Hispanic	121 (2.4%)	1,315 (6.1%)
White	1,062 (82.3%)	4,637 (65.7%)
Black	352 (8.0%)	2,562 (11.8%)
Other race	100 (4.6%)	1,077 (7.2%)
Education, n (%)			0.002*
Under high school	518 (18.9%)	2,877 (16.6%)
High school level	454 (25.5%)	2,584 (21.8%)
College level or above	794 (55.6%)	6,109 (61.6%)
Marriage, n (%)			<0.001*
Married	1,128 (70.6%)	6,895 (63.0%)
Widowed	173 (7.0%)	505 (2.8%)
Divorced/separated	309 (14.3%)	1,637 (12.6%)
Never married	155 (8.1%)	2,524 (21.6%)
FPL, n (%)			0.033*
Q1: 0%–50%	95 (3.4%)	785 (5.1%)
Q2: 51%–100%	254 (8.9%)	1,546 (10.0%)
Q3: 101%–130%	193 (7.0%)	1,045 (6.4%)
Q4: >130%	1,090 (80.7%)	7,201 (78.5%)
Mineral dusts exposure, n (%)			<0.001*
Non-exposure	1,067 (63.6%)	8,003 (72.6%)
Short-term	130 (7.0%)	962 (8.9%)
Intermediate	170 (9.6%)	1,049 (8.9%)
Long-term	360 (19.9%)	1,102 (9.6%)
Organic dusts exposure, n (%)			<0.001*
Non-exposure	1,289 (73.8%)	8,942 (79.9%)
Short-term	87 (4.9%)	750 (7.2%)
Intermediate	128 (7.6%)	748 (6.8%)
Long-term	234 (13.7%)	693 (6.1%)
Exhaust fumes exposure, n (%)			<0.001*
Non-exposure	1,162 (66.7%)	8,669 (77.5%)
Short-term	111 (6.6%)	738 (7.0%)
Intermediate	150 (8.7%)	858 (7.8%)
Long-term	316 (18.1%)	874 (7.7%)
Other fumes exposure, n (%)			0.001*
Non-exposure	1,095 (63.6%)	7,978 (71.7%)
Short-term	142 (8.3%)	1,041 (9.8%)
Intermediate	179 (10.3%)	1,063 (9.2%)
Long-term	322 (17.7%)	1,056 (9.3%)
Second-hand smoke exposure, n (%)			0.032*
No	660 (83.1%)	6,166 (86.1%)
Yes	142 (16.9%)	1,062 (13.9%)

Notes: Data are weighted according to the National Health and Nutrition Examination Survey protocol (unweighted n=13,336, weighted N=179,998,708). Values are expressed as mean (SEs) for continuous variables and unweighted counts (weighted %) for categorical variables.

* Significant difference between the two groups, P<0.05.

Abbreviations: COPD, chronic obstructive pulmonary disease; FPL, federal poverty level; SE, standard error.

Table 2 Logistic regression analysis of factors associated with occupational exposure and COPD

Occupational exposure	Crude OR (95% CI)	Model 1: adjusted OR (95% CI)a	Model 2: adjusted OR (95% CI)b
Mineral dusts exposure
Non-exposure	Reference	Reference	Reference
Short-term	0.896 (0.689, 1.166)	1.001 (0.743, 1.349)	0.970 (0.700, 1.344)
Intermediate	1.228 (0.937, 1.611)	1.256 (0.922, 1.711)	1.237 (0.945, 1.618)
Long-term	2.364 (1.950, 2.865)	1.179 (0.932, 1.492)	1.120 (0.892, 1.406)
Organic dusts exposure
Non-exposure	Reference	Reference	Reference
Short-term	0.746 (0.579, 0.960)	0.998 (0.737, 1.350)	0.979 (0.695, 1.379)
Intermediate	1.215 (0.956, 1.545)	1.314 (1.021, 1.692)	1.366 (1.036, 1.801)
Long-term	2.427 (2.006, 2.937)	1.350 (1.045, 1.744)	1.298 (1.002, 1.681)
Exhaust fumes exposure
Non-exposure	Reference	Reference	Reference
Short-term	1.084 (0.853, 1.379)	1.211 (0.915, 1.604)	1.244 (0.907, 1.706)
Intermediate	1.294 (1.027, 1.631)	1.306 (1.000, 1.706)	1.223 (0.903, 1.657)
Long-term	2.728 (2.301, 3.233)	1.342 (1.085, 1.660)	1.270 (1.034, 1.561)
Other fumes exposure
Non-exposure	Reference	Reference	Reference
Short-term	0.956 (0.731, 1.251)	1.030 (0.755, 1.406)	0.951 (0.672, 1.346)
Intermediate	1.267 (0.972, 1.650)	1.279 (0.951, 1.719)	1.133 (0.830, 1.545)
Long-term	2.144 (1.752, 2.623)	1.053 (0.840, 1.321)	0.977 (0.765, 1.247)
Second-hand smoke
No	Reference	Reference	Reference
Yes	1.259 (1.021, 1.552)	1.231 (0.971, 1.560)	1.216 (0.978, 1.512)

Notes:

a Adjustment for the following baseline covariates of demographic factors: age, gender, race, education, marital status, smoking and family income/poverty ratio.

b Adjustment for covariates in the first model + FeNO. Significant values are shown in bold (P<0.05).

Abbreviations: COPD, chronic obstructive pulmonary disease; OR, odds ratio; CI, confidence interval; FeNO, fractional exhaled nitric oxide.

Table 3 Associations between occupational exposure and COPD by FeNO levels (cutoff point: 50 ppb)a

Occupational exposure	Group 1, FeNO ≤50 ppb (n=11,687)	Group 2, FeNO >50 ppb (n=372)
Mineral dusts
Non-exposure	Reference	Reference
Short-term	0.940 (0.672, 1.315)	1.580 (0.431, 5.794)
Intermediate	1.300 (0.981, 1.722)	0.337 (0.108, 1.054)
Long-term	1.163 (0.928, 1.456)	0.242 (0.058, 1.010)
Organic dusts
Non-exposure	Reference	Reference
Short-term	0.964 (0.671, 1.386)	1.222 (0.390, 3.827)
Intermediate	1.396 (1.045, 1.863)	0.574 (0.165, 1.999)
Long-term	1.361 (1.046, 1.771)	0.058 (0.010, 0.350)
Exhaust fumes
Non-exposure	Reference	Reference
Short-term	1.257 (0.904, 1.746)	1.339 (0.334, 5.370)
Intermediate	1.238 (0.895, 1.712)	1.073 (0.305, 3.774)
Long-term	1.314 (1.061, 1.629)	0.210 (0.058, 0.757)
Other fumes
Non-exposure	Reference	Reference
Short-term	0.962 (0.683, 1.356)	0.749 (0.196, 2.857)
Intermediate	1.181 (0.862, 1.619)	0.193 (0.035, 1.065)
Long-term	1.005 (0.789, 1.280)	0.574 (0.138, 2.393)
Second-hand smoke
No	Reference	Reference
Yes	1.318 (1.054, 1.649)	0.389 (0.141, 1.072)

Notes:

a Adjustment for the following baseline covariates: age, gender, race, education, marital status, smoking and family income/poverty ratio. Significant values in bold (P<0.05).

Abbreviations: COPD, chronic obstructive pulmonary disease; FeNO, fractional exhaled nitric oxide.

Table 4 Associations between FeNO >50 ppb and occupational exposure in respondents with COPD

Occupational exposure	OR (95% CI)
Mineral dusts exposure
Non-exposure	Reference
Short-term	1.724 (0.670, 4.438)
Intermediate	0.770 (0.290, 2.040)
Long-term	0.315 (0.131, 0.760)
Organic dusts
Non-exposure	Reference
Short-term	1.238 (0.431, 3.555)
Intermediate	0.452 (0.159, 1.290)
Long-term	0.115 (0.034, 0.395)
Exhaust fumes
Non-exposure	Reference
Short-term	0.685 (0.220, 2.132)
Intermediate	1.377 (0.390, 4.854)
Long-term	0.168 (0.058, 0.489)
Other fumes
Non-exposure	Reference
Short-term	1.067 (0.400, 2.841)
Intermediate	0.178 (0.035, 0.901)
Long-term	0.573 (0.165, 1.985)

Note: Significant values are shown in bold (P<0.05).

Abbreviations: FeNO, fractional exhaled nitric oxide; COPD, chronic obstructive pulmonary disease; OR, odds ratio; CI, confidence interval.