Relationship of airflow limitation severity with work productivity reduction and sick leave in a Japanese working population

Figures & data

Figure 1 Flowchart of selecting the subjects with airflow limitation or normal lung function.

Abbreviations: FEV₁/FVC, forced expiratory volume in 1 second to forced vital capacity; FEV₁% predicted, forced expiratory volume in 1 second as percentage of predicted.

Table 1 The characteristics of the study subjects

Characteristics	Normal lung function, n=1,280	Mild AL, n=48	Moderate-to-severe AL, n=50	P-value
Sex
Male, n (%)	836 (65.3)	38 (79.2)	47 (94.0)	<0.001
Female, n (%)	444 (34.7)	10 (20.8)	3 (6.0)
Age, years	49.3 (8.8)	53.0 (9.5)*	55.9 (9.7)**	<0.001
Height, cm	165.7 (8.2)	168.0 (8.4)	167.9 (7.7)	0.027
Weight, kg	64.1 (11.3)	64.4 (11.1)	68.2 (12.4)*	0.112
BMI, kg/m^2	23.3 (3.2)	22.7 (3.0)	24.1 (3.2)	0.048
Smoking status
Never, n (%)	657 (51.3)	16 (33.3)	12 (24.0)
Former, n (%)	363 (28.4)	12 (25.0)	20 (40.0)
Current, n (%)	260 (20.3)	20 (41.7)	18 (36.0)	<0.001
Pack-years	10.0 (15.3)	18.0 (24.0)*	22.2 (26.6)**	<0.001
Lung function
FEV1, mL	3,081.3 (631.1)	2,885.0 (596.6)	2,281.4 (517.0)**,##	<0.001
FVC, mL	3,861.1 (799.2)	4,368.5 (896.8)**	3,715.8 (829.5)##	<0.001
FEV1/FVC, %	80.1 (5.3)	66.1 (2.4)**	61.8 (6.9)**,##	<0.001
FEV1%, predicted, %	98.6 (11.1)	89.1 (7.4)**	69.4 (9.7)**,##	<0.001
Clinical information
Hypertension, n (%)	410 (32.0)	14 (29.2)	23 (46.0)	0.104
Dyslipidemia, n (%)	566 (44.2)	21 (43.8)	30 (60.0)	0.088
Hyperglycemia, n (%)	167 (13.0)	8 (16.7)	12 (24.0)	0.070
Sleep duration
6–8 h, n (%)	1,088 (85.0)	39 (81.2)	42 (84.0)
<6 h, n (%)	182 (14.2)	8 (16.7)	5 (10.0)
>8 h, n (%)	10 (0.8)	1 (2.1)	3 (6.0)	0.006
Work hours per day
≤8 h, n (%)	674 (52.6)	23 (47.9)	26 (52.0)
>8≤10 h, n (%)	440 (34.4)	16 (33.3)	19 (38.0)
>10 h, n (%)	166 (13.0)	9 (18.8)	5 (10.0)	0.743
Smoking environment at workplace, n=1,307a	n=1,216a	n=43a	n=48a
Smoke-free, n (%)	403 (33.2)a	10 (23.3)a	13 (27.1)a
Restrictive, n (%)	707 (58.1)a	28 (65.1)a	23 (47.9)a
Nonrestrictive, n (%)	106 (8.7)a	5 (11.6)a	12 (25.0)a	0.010
Productivity loss at workb
Quality, n (%)	518 (40.5)	22 (45.8)	26 (52.0)	0.211
Quantity, n (%)	515 (40.2)	20 (41.7)	27 (54.0)	0.150
Sick leave, n=1,111c	n=1,038c	n=36c	n=37c
Sick leave, n (%)	410 (39.5)c	15 (41.7)c	20 (54.1)c	0.203

Notes: Total number of study subjects =1,378. Data presented are mean (standard deviation) unless otherwise stated.

* P<0.05,

** P<0.001 compared with normal lung function;

## P<0.001 compared with mild airflow limitation. Airflow limitation was defined as FEV₁/FVC <0.7. Pack-years: (number of cigarettes smoked per day × number of years smoked)/20.

a Smoking environment at workplace was only recorded for 1,307 of the 1,378 total subjects, 1,216 of the 1,280 normal lung function, 43 of the 48 mild AL, and 48 of the 50 moderate-to-severe.

b Total number of study subjects for productivity loss at work was 1,378.

c Sick leave was only recorded for 1,111 of 1,378 total subjects, 1,038 of the 1,280 normal lung function, 36 of the 48 mild AL, and 37 of the 50 moderate-to-severe.

Abbreviations: AL, airflow limitation; BMI, body mass index; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; FEV₁/FVC, forced expiratory volume in 1 second to forced vital capacity; FEV₁% predicted, forced expiratory volume in 1 second as percentage of predicted; h, hours.

Table 2 Multivariable adjusted OR (95% CI) for quality of work productivity at work and airflow limitation severity

	Normal lung function, n=1,280	Mild AL, n=48	P-value	Moderate-to-severe AL, n=50	P-value
Crude	Reference	1.25 (0.70–2.22)	0.46	1.59 (0.91–2.81)	0.11
Model 1: sex, age, BMI	Reference	1.40 (0.78–2.51)	0.27	1.97 (1.10–3.52)	0.02
Model 2: model 1 + smoking status	Reference	1.40 (0.78–2.52)	0.27	2.01 (1.12–3.60)	0.02
Model 3: model 2 + hypertension, hyperglycemia, dyslipidemia	Reference	1.40 (0.78–2.53)	0.26	1.99 (1.11–3.58)	0.02
Model 4: model 3 + sleep duration	Reference	1.38 (0.76–2.49)	0.29	1.95 (1.08–3.51)	0.03
Model 5: model 4 + work hours per day	Reference	1.35 (0.76–2.45)	0.32	1.94 (1.07–3.50)	0.03
Model 6: model 5 + smoking environment at workplace	Reference	1.51 (0.81–2.82)	0.20	2.04 (1.12–3.71)	0.02

Note: Total number of study subjects =1,378.

Abbreviations: AL, airflow limitation; OR, odds ratio; CI, confidence interval; BMI, body mass index.

Table 3 Multivariable adjusted OR (95% CI) for quantity of work productivity at work and airflow limitation severity

	Normal lung function, n=1,280	Mild AL, n=48	P-value	Moderate-to-severe AL, n=50	P-value
Crude	Reference	1.06 (0.59–1.90)	0.84	1.74 (0.99–3.08)	0.06
Model 1: sex, age, BMI	Reference	1.20 (0.66–2.17)	0.55	2.16 (1.21–3.87)	0.01
Model 2: model 1 + smoking status	Reference	1.17 (0.64–2.12)	0.61	2.17 (1.21–3.90)	0.01
Model 3: model 2 + hypertension, hyperglycemia, dyslipidemia	Reference	1.17 (0.64–2.12)	0.61	2.16 (1.20–3.89)	0.01
Model 4: model 3 + sleep duration	Reference	1.15 (0.63–2.09)	0.65	2.11 (1.17–3.81)	0.01
Model 5: model 4 + work hours per day	Reference	1.12 (0.61–2.04)	0.72	2.10 (1.16–3.80)	0.01
Model 6: model 5 + smoking environment at workplace	Reference	1.31 (0.70–2.46)	0.40	2.19 (1.20–4.00)	0.01

Note: Total number of study subjects =1,378.

Abbreviations: AL, airflow limitation; OR, odds ratio; CI, confidence interval; BMI, body mass index.

Table 4 Multivariable adjusted OR (95% CI) for the presence of sick leave and airflow limitation severity

	Normal lung function, n=1,038	Mild AL, n=36	P-value	Moderate-to-severe AL, n=37	P-value
Crude	Reference	1.09 (0.56–2.15)	0.79	1.80 (0.93–3.48)	0.08
Model 1: sex, age, BMI	Reference	1.23 (0.62–2.44)	0.56	2.45 (1.24–4.86)	0.01
Model 2: model 1 + smoking status	Reference	1.19 (0.59–2.36)	0.63	2.40 (1.21–4.76)	0.01
Model 3: model 2 + hypertension, hyperglycemia, dyslipidemia	Reference	1.22 (0.61–2.43)	0.58	2.43 (1.22–4.85)	0.01
Model 4: model 3 + sleep duration	Reference	1.21 (0.61–2.43)	0.59	2.50 (1.25–5.00)	0.01
Model 5: model 4 + work hours per day	Reference	1.24 (0.62–2.49)	0.55	2.51 (1.25–5.02)	0.01
Model 6: model 5 + smoking environment at workplace	Reference	1.36 (0.67–2.76)	0.40	2.69 (1.33–5.44)	0.006

Notes: Total number of study subjects was 1,111 including 1,038 normal lung function, 36 mild AL, and 37 moderate-to-severe AL.

Abbreviations: AL, airflow limitation; OR, odds ratio; CI, confidence interval; BMI, body mass index.