Socioeconomic outcome of subjects experiencing asthma symptoms at work

Demographic characteristics at initial assessment

	Occupational asthma	Subjects with negative SIC
Subjects n	86	71
Sex female	33 (38)	25 (35)
Age yr^#,¶	35 (32–47)	46 (34–54)
Education level^†
≤9 yrs	22 (26)	25 (36)
10–12 yrs	33 (38)	33 (47)
>12 yrs	31 (36)	12 (17)
Unskilled labour^§	31 (36)	43 (61)
Smoking habits^ƒ
Smokers	8 (9)	13 (18)
Exsmokers	21 (24)	25 (35)
Atopy	52 (60)	38 (53)
Referral by WCB	51 (59)	46 (64)
Agents suspected of causing symptoms n
Latex	30	8
Flour	14	16
Wood dust	9	11
Isocyanates	7	11
Metals, welding	10	1
Paints, resins, glues	1	12
Enzymes	3	2
Aldehydes	1	4
Antibiotics	1	2
Persulphate salts	3	1
Various chemical agents	6	5
Various animal or vegetal agents	2	0

Data are presented as n (%) unless otherwise stated
SIC: specific inhalation challenge
WCB: Workers Compensation Board
^#: median (25–75th percentiles)
^¶: p=0.05
⁺: p=0.018
^§: p=0.002
^ƒ: p=0.038 comparing subjects with occupational asthma and those with negative S/C

Clinical and functional characteristics at initial assessment

	Occupational asthma	Subjects with negative SIC
Subjects n	86	71
Asthma before employment n (%)^¶	17 (20)	5 (7)
Duration of exposure before onset of workrelated asthma symptoms month^#	82 (26–164)	93 (20–195)
Duration of asthma before diagnosis month^#	46 (24–77)	36 (19–68)
Removal from work before SIC	46 (53)	40 (56)
Time lapse from last work exposure to SIC month^#	0.6 (0.1–16.5)	2 (0.1–17.0)
Duration of followup month^#	40 (28–67)	47 (29–66)
Asthmaseverity score^#	8 (5–9)	7 (5–8)
FEV₁ % pred^#	93 (83–102)	93 (81–100)
FEV₁ <80% pred	12 (14)	17 (24)
FEV₁/FVC %^#	78 (71–81)	75 (69–81)
Histamine PC₂₀, mg·mL^−1#,†	0.72 (0.09–2.57)	1.46 (0.23–5.27)
≥16 mg·mL⁻¹	6 (7)	5 (7)
2–16 mg·mL⁻¹	19 (22)	23 (32)
0.25–2 mg·mL⁻¹	32 (37)	24 (34)
<0.25 mg·mL⁻¹	29 (34)	19 (27)

Data are presented as n (%) or n (range)
SIC: specific inhalation challenge
FEV₁: forced expiratory volume in one second
FVC: forced vital capacity
PC₂₀: provocation concentration causing a 20% fall in FEV₁
^#: median (25th–75th percentiles)
^¶: p=0.022
^†: 0.021 comparing subjects with occupational asthma and those with negative SIC

Employment, exposure, and income status at followup

	Occupational asthma	Subjects with negative SIC
Subjects n	86	71
Asthmarelated work disability^#,ƒ	62 (72)	38 (54)
Working status
Currently working	53 (62)	38 (54)
Same job, same employer	18 (21)	17 (24)
Same job, different employer	4 (5)	3 (4)
Different job, same employer	13 (15)	7 (10)
Different job, different employer	18 (21)	11 (15)
Not working	33 (38)	33 (46)
Unemployment	22 (26)	15 (21)
Chronic sick leave	9 (10)	7 (10)
Retirement	2 (2)	11 (15)^§
Exposure to the causal agent^##
Cessation of exposure	58 (67)	51 (72)
Reduction of exposure	22 (26)	6 (8)
Persistence of exposure	6 (7)	14 (20)
Income status
Perceived change in income
No reduction	31 (36)	26 (37)
Slight reduction	9 (10)	6 (8)
Major reduction	45 (52)	36 (51)
Actual reduction in income % from initial^¶	22 (0–44)	23 (0–41)
Compensation status
Claim for compensation***	83 (96)	55 (78)
Receiving compensation	75 (92)	2 (3)
Income loss offset by compensation	10/45⁺ (22)	1/2

SIC: specific inhalation challenge
Data are presented as n (%) unless otherwise stated
^#: defined as ever having changed jobs or left work due to asthma
^¶: median (25th–75th percentiles)
^†: number of subjects who reported a loss of income and who answered this question
^§: p=0.005 when comparing the proportion of retired workers in both groups
^ƒ: p=0.016
^##: p = 0.003
***: p<0.001 comparing subjects with occupation asthma and those with negative SIC

Odds ratios (or) for being employed at followup

Variable	OR	95% CI
Age yrs***	0.91	0.87–0.95
Level of education^#
≤9 yrs, 10–12 yrs, >12 yrs	2.21	1.25–3.89
SIC result
positive versus negative	0.62	0.27–1.45
Asthmaseverity score 28point scale	0.91	0.78–1.06
Log PC₂₀ Loge unit	0.91	0.75–1.12
Time elapsed since onset of workrelated symptoms months	0.99	0.99–1.02
Company size
number of workers ≤10, 10–100, >100	0.98	0.60–1.62

CI: confidence interval
SIC: specific inhalation challenge
PC₂₀: provocation concentration causing a 20% fall in forced expiratory volume in one second
***: p<0.001
^#: p=0.006