Occupational Chronic Obstructive Pulmonary Disease in a Danish Population-Based Study

Figures & data

Figure 1.  Flow chart of the study enrolment population.

Figure 2.  Occupational exposure in males (n) and females (n) (N = 4717). Vapour, Gas, Dust and/or Fume (VGDF) exposure: Low, “Only having specific low exposure”; Medium, “Having specific medium exposure but no specific high exposure”; and High, “Having any specific high exposure” Organic dust, inorganic dust, fume/gas and vapours occupational exposure means of duration: Low, <5 years in exposed job (excluding no exposure); Medium, 5–14 years in exposed job; and High, ≥15 years in exposed job.

Table 1.  Description of the study population, N = 4717

Characteristic	Female		Male		Total
	n	(%)	n	(%)	n	(%)
Age
Age groups
45–54 years	509	(31)	400	(13)	909	(19)
55–64 years	420	(26)	649	(21)	1069	(23)
65–74 years	426	(26)	1359	(44)	1785	(38)
75–84 years	271	(17)	683	(22)	954	(20)
Total	1626	3091	4717
Mean age (SD)	62.4	(10.8)	67.0	(9.3)	65.5	(10.1)
Occupational exposure
VGDF duration of occupational exposure (n = 4474)
No exposure	1226	(81)	1104	(37)	2330	(52)
Only low^a exposures	61	(4)	309	(10)	370	(8)
Medium^b exposure (and no high)	63	(4)	360	(12)	423	(9)
Any high^c exposure	155	(10)	1196	(40)	1351	(30)
Any organic dust (n = 3883)	244	(19)	1469	(56)	1713	(44)
Any inorganic dust (n = 3776)	9	(1)	563	(24)	572	(15)
Any fume/gas (n = 3826)	23	(2)	384	(16)	407	(11)
Any vapour (n = 3701)	17	(1)	152	(6)	169	(5)
Smoking habits
Status (n = 4692)
Never smokers	722	(45)	853	(28)	1575	(34)
Ex-smokers	537	(33)	1490	(48)	2027	(43)
Current smokers	354	(22)	736	(24)	1090	(23)
Duration (n = 4614)
Mean smoked years (SD)	15.4	(17.9)	25.5	(20.8)	22.0	(20.4)
Cumulated smoking (n = 4371)
Mean smoked pack-years (SD)	8.7	(12.7)	26.0	(29.8)	20.1	(26.6)

^aLow: Exposure but < 5 years.

^bMedium: 5 to 14 years of exposure.

^cHigh: ≥15 years of exposure.

VGDF: Vapour, gas, dust and fume.

SD: Standard deviation.

All variables between sexes, p < 0.001.

Table 2.   The study and age-standardised prevalence of COPD by sex and age group (n = 4697)

	COPD defined by LLN^a
	Female			Male			Total
	n	%	(95% CI)	n	%	(95% CI)	n	%	(95% CI)
Age groups
45–54	17	3.4	(1.8–4.9)	13	3.3	(1.5–5.0)	30	3.3	(2.1–4.5)
55–64	18	4.3	(2.4–6.3)	26	4.0	(2.5–5.5)	44	4.1	(2.9–5.3)
65–74	21	5.0	(2.9–7.0)	105	7.8	(6.3–9.2)	126	7.1	(5.9–8.3)
75–84	20	7.5	(4.3–10.6)	59	8.7	(6.6–10.8)	79	8.3	(6.6–10.1)
All ages	76	4.7	(3.7–5.7)	203	6.6	(5.7–7.5)	279	5.9	(5.3–6.6)
Age-standardised^b	4.6	(4.6–4.6)		5.0	(5.0–5.0)			5.0	(5.0–5.0)

COPD: Chronic Obstructive Pulmonary Disease.

CI: Confidence Interval.

^aLLN: Lower Limit of Normal; FEV₁/FVC z-score <−1.96 and FEV₁ z-score <–2.0.

^bPrevalence age-standardised to the Danish population, January 2006.

Table 3.  Comparison of LLN and GOLD methods to define COPD by spirometry in the study population

		GOLD		Total
		Normal or GOLD I	GOLD II or more severe^a
LLN	Normal or mild COPD	4071	156	4227
	Moderate or more severe^b	17	230	247
Total	4088	386	4474

LLN: Lower Limit of Normal.

GOLD: Global Initiative for Chronic Obstructive Lung Diseases.

COPD: Chronic Obstructive Pulmonary Disease.

^aFEV₁/FVC ratio<0.70 and FEV₁< 80% of the predicted value.

^bFEV₁/FVC z-score <−1.96 and FEV₁ z-score <−2.0.

Table 4.  Occupational and covariates associations to COPD in the population-based study.

	Odds Ratio (OR)
	Crude		Adjusted^a
	OR	95% CI	OR	95% CI
VGDF occupational exposure	n = 4457		n = 4132
No	1.00	Reference	1.00	Reference
Low	1.08	(0.66–1.78)	1.05	(0.61–1.80)
Medium	1.87	(1.27–2.77)	1.61	(1.03–2.51)
High	1.55	(1.17–2.05)	1.38	(0.99–1.93)
Score test for trend	p < 0.001		p = 0.031^b
Covariates
<10 pack-years			1.00	Reference
10–20 pack-years			2.60	(1.54–4.38)
>20 pack-years			7.26	(4.95–10.66)
Age 45–54			1.00	Reference
Age 55–64			1.22	(0.73–2.02)
Age 65–74			2.09	(1.33–3.29)
Age 75–84			2.28	(1.38–3.76)
Males			1.00	Reference
Females			1.78	(1.24–2.56)
Organic dust exposure	n = 3867		n = 3607
No	1.00	Reference	1.00	Reference
Low	1.22	(0.73–2.05)	1.15	(0.65–2.03)
Medium	1.49	(0.95–2.33)	1.24	(0.74–2.07)
High	1.50	(1.10–2.04)	1.56	(1.09–2.24)
Score test for trend	p = 0.006		p = 0.017^b
Covariates
<10 pack-years			1.00	Reference
10–20 pack-years			2.36	(1.34–4.16)
>20 pack-years			6.82	(4.55–10.22)
Age 45–54			1.00	Reference
Age 55–64			1.23	(0.71–2.14)
Age 65–74			2.10	(1.28–3.44)
Age 75–84			2.13	(1.23–3.69)
Males			1.00	Reference
Females			1.89	(1.30–2.77)

COPD: Chronic Obstructive Pulmonary Disease.

CI: Confidence Interval.

VGDF: Vapour, gas, dust and fume.

Bold estimates: Beyond the significance level of 5%.

^aRandom effect logistic regression adjusted for; Pack-year group: < 10, 10–20, and > 20 smoked pack-years; Age group: 45–54, 55–64, 65–74, 75–84 years of age; Sex; General practitioner practice (random variable).

^bWithout the random variable.