Combined Effect of Smoking and Occupational Exposure to Dusts, Gases or Fumes on the Incidence of COPD

Figures & data

Table 1.  Descriptive statistics of the study population

	Male	Female	All
Age: mean (SD)	53.3 (12.6)	52.8 (13.0)	53.0 (12.8)
Smoking status 2007
Nonsmoker	40.2%	54.8%	48.8%
Former smoker	32.2%	24.5%	27.6%
Current smoker	27.6%	20.7%	23.6%
Under 5 cigarettes/day	6.9%	4.9%	5.7%
5–14 cigarettes/day	8.8%	9.4%	9.1%
15–24 cigarettes/day	9.2%	5.2%	6.9%
25 or over cigarettes/day	2.7%	1.2%	1.8%
Self reported occupational exposure	30.8%	22.3%	25.7%
Physician-diagnosed asthma	6.4%	9.3%	8.1%
Physician-diagnosed COPD	3.6%	3.3%	3.4%
Use of asthma medication	5.8%	9.9%	8.2%

Figure 1.  Adjusted odds ratios (OR) between 2007 and 1996 for symptoms suggestive of obstructive airways diseases assessed with a multiple logistic regression model adjusted for categorized age decade, gender, and smoking history.

Table 2.  Prevalence of respiratory symptoms in subjects with and without incident COPD in 2007 and the odds ratios for respiratory symptoms reported in 1996 predicting incident COPD in 2007

		Prevalence of symptom
		1996		2007		1996 risk factor for incident COPD in 2007
		No COPD	Incident COPD in 2007	No COPD	Physician-diagnosed COPD	OR (95% CI)	p-value
SOB 10 yrs		14.8%	31.4%	18.2%	61.4%	2.634 (1.824–3.804)	p < 0.001
SOB 12 mo		10.6%	22.9%	11.9%	48.6%	2.503 (1.666–3.762)	p < 0.001
Longstanding cough		17.0%	37.9%	16.3%	53.6%	2.973 (2.092–4.226)	p < 0.001
Phlegm		22.7%	48.6%	19.8%	62.1%	3.209 (2.284–4.507)	p < 0.001
Phlegm months		12.9%	34.3%	12.6%	52.9%	3.525 (2.456–5.058)	p < 0.001
Chronic productive cough		8.7%	31.4%	8.9%	47.9%	4.837 (3.329–7.029)	p < 0.001
Recurrent wheeze		4.1%	17.1%	4.5%	36.4%	4.856 (3.044–7.746)	p < 0.001
Past year wheeze		17.5%	30.0%	15.5%	46.4%	2.022 (1.396–2.930)	p < 0.001
Wheeze with dyspnea		7.8%	17.1%	7.7%	37.1%	2.440 (1.548–3.844)	p < 0.001
Wheeze outside colds		10.6%	20.2%	10.4%	43.6%	2.106 (1.375–3.226)	p = 0.001
Waking up with difficulty to breathe		22.1%	45.7%	19.0%	45.7%	2.976 (2.116–4.185)	p < 0.001
Dyspnea when walking flat		10.3%	27.9%	12.1%	50.7%	3.380 (2.303–4.960)	p < 0.001
Factors provoking
	Excercise	14.5%	35.7%	15.9%	57.1%	3.278 (2.294–4.684)	p < 0.001
	Cold air	9.8%	25.7%	11.1%	45.7%	3.169 (2.139–4.696)	p < 0.001
	Excercise in cold	21.3%	40.7%	21.6%	57.1%	2.531 (1.791–3.576)	p < 0.001
	Dusty surroundings	30.2%	48.6%	29.3%	60.0%	2.188 (1.560–3.069)	p < 0.001
	Smoke	20.9%	32.9%	19.8%	42.9%	1.848 (1.288–2.651)	p = 0.001
	Exhaust	18.2%	32.1%	16.3%	41.4%	2.133 (1.482–3.069)	p < 0.001
	Smells	19.8%	32.1%	19.5%	40.7%	1.916 (1.332–2.755)	p < 0.001
	Pollen	14.7%	22.9%	16.4%	29.3%	1.716 (1.146–2.571)	p = 0.009
	Animal contact	9.8%	21.4%	10.1%	22.1%	2.511 (1.655-3.811)	p < 0.001

Figure 2.  Incidence rate of COPD (cases/1000/year) by different smoking categories and by a) self-reported OE to dust, gases or fumes, and b) cumulative exposure categories (none, low, high) according job-exposure matrix.

Table 3.  Multiple logistic regression model* for risk factors for incident COPD in the population

	Prevalence of risk factor
	Subjects with incident COPD	Subjects without incident COPD	OR for incident COPD* OR (95% CI)	p-value
Gender (male)	42.1%	40.6%	0.963 (0.670–1.385)	p = n.s.
Age over 50	79.3%	55.5%	3.419 (2.222–5.261)	p < 0.001
Smoking history (1996 questionnaire)
Nonsmoker	23.6%	52.8%	1
Former smoker	19.3%	17.4%	1.931 (1.139–3.275)	p = 0.015
Current smoker	57.1%	29.8%	4.403 (2.889–6.710)	p < 0.001
Family history of asthma (1996)	23.6%	17.9%	0.958 (0.618–1.485)	p = n.s.
Family history of arc (1996)	38.6%	34.2%	1.315 (0.880–1.965)	p = n.s.
Family history of COPD (1996)	16.4%	6.3%	2.084 (1.268–3.426)	p = 0.004
Ever asthma (1996)	14.3%	6.1%	2.283 (1.350–3.862)	p = 0.002
Ever arc (1996)	41.4%	36.6%	1.128 (0.764–1.666)	p = n.s.
Self-reported occupational exposure (2007)	44.3%	25.1%	2.140 (1.503–3.046)	p < 0.001

arc = allergic rhinoconjunctivitis; COPD = chronic obstructive pulmonary disease.*All variables in the table were included in the model. Associations are presented as Odds Ratios (OR) with 95% confidence intervals (95% CI).

Table 4.  Crude incidence rate and risk of incident physician-diagnosed chronic obstructive pulmonary disease (COPD) in relation to cigarette smoking and occupational exposure to dusts, gases or fumes

	Crude incidence rate (cases/1000/year)	Unadjusted OR (95% CI)	P-value	Adjusted OR (95% CI)	p-value
Whole population at risk
Self-reported OE exposure	5.36	2.375 (1.688–3.341)	<0.001	2.415 (1.709–3.412)	0.001
JEM-based exposure
None	2.61	1		1
Low	3.96	1.541 (1.030–2.308)	0.036	1.565 (1.040–2.356)	0.032
High	7.07	2.854 (1.608–5.065)	<0.001	1.905 (1.047–3.463)	0.035
Smoking status 1996
Nonsmoker	1.42	1		1
Former smoker	3.45	2.489 (1.489–4.170)	0.001	2.125 (1.256–3.595)	0.005
Current smoker	5.80	4.293 (2.844–6.481)	<0.001	5.312 (3.475–8.120)	<0.001
Ever smoker 2007	4.92	4.168 (2.727–6.372)	<0.001	4.500 (2.920–6.934)	<0.001
Population at risk excluding symptomatics^#
Self-reported OE exposure	4.63	2.327 (1.600–3.385)	<0.001	2.330 (1.595–3.404)	<0.001
JEM-based exposure
None	2.36	1		1
Low	3.56	1.534 (0.994–2.366)	0.053	1.528 (0.985–2.368)	0.058
High	5.02	2.199 (1.111–4.350)	0.024	1.456 (0.718–2.950)	0.297
Smoking status 1996
Nonsmoker	1.33	1		1
Former	3.33	2.566 (1.498–4.394)	0.001	2.149 (1.242–3.718)	0.006
Current	4.72	3.689 (2.369–5.746)	<0.001	4.355 (2.764–6.862)	<0.001
Ever smoker 2007	4.19	3.692 (2.361–5.774)	<0.001	3.834 (2.433–6.042)	<0.001

OR = odds ratio; OE = occupational exposure; JEM = job exposure matrix.*Model containing adjustment for age in 2007 (continuous variable) and sex.^#Adjusted sample excluding all subjects with longstanding cough and dyspnea in 1996 survey.