Relationship between depression and lung function in the general population in Korea: a retrospective cross-sectional study

Figures & data

Figure 1 Flow chart of patient selection for the study.

Abbreviation: BDI, Beck Depression Inventory.

Table 1 Baseline characteristics of the study population (n=3,321)

Variable	Total (N=3,321)	Before propensity score matching (n=3,321)			After propensity score matching (n=744)
		Without depression (n=2,887)	Depression (n=434)	P-value	Without depression (n=372)	Depression (n=372)	P-value
BDI score	7.9±6.8	5.9±4.1	21.6±5.7	<0.001	6.1±4.3	21.7±5.8	<0.001
Age (years)	52.4±7.3	52.0±7.1	54.7±8.3	<0.001	55.2±8.2	54.7±8.3	0.463
Sex, male, n (%)	1,740 (52.4)	1,567 (54.3)	173 (39.9)	<0.001	154 (41.5)	148 (39.9)	0.662
BMI (kg/m^2)	24.5±2.7	24.5±2.7	24.2±2.8	0.015	24.4±2.7	24.2±2.5	0.213
Smoking (baseline)				<0.001			0.385
Never smoker	1,947 (58.6)	1,663 (57.6)	284 (65.4)		234 (62.9)	243 (65.4)
Former smoker	779 (23.5)	716 (24.8)	63 (14.5)		67 (18.0)	54 (14.5)
Current smoker	594 (17.9)	507 (17.6)	87 (20.0)		71 (19.1)	75 (20.2)
Pack-years of smoking	23.2±16.4	22.6±16.0	27.6±18.9	0.003	24.0±15.9	27.6±18.9	0.073
Occupation				<0.001			0.052
White collar joba	475 (14.3)	425 (14.8)	43 (7.4)		42 (11.3)	35 (9.4)
Blue collar jobb or unemployed	2,857 (86.0)	2,455 (85.2)	402 (92.6)		330 (88.7)	337 (90.6)
Marriage				0.212			0.551
Singlec	220 (6.6)	181 (6.3)	39 (9.0)		24 (6.5)	33 (9.0)
Married	3,101 (93.4)	2,706 (93.7)	395 (91.0)		348 (93.5)	339 (91.0)
Underlying diseases
Hypertension	394 (11.9)	334 (11.6)	60 (13.8)	0.176	51 (13.8)	51 (13.8)	1.000
Diabetes mellitus	181 (5.5)	153 (5.3)	28 (6.5)	0.324	23 (6.2)	24 (6.5)	0.889
Cardiovascular disease	16 (0.5)	14 (0.5)	2 (0.5)	0.946	3 (0.9)	2 (0.5)	0.413
Lung function
FEV1 (L)	2.98±0.65	3.01±0.64	2.76±0.63	<0.001	2.65±0.63	2.84±0.62	0.039
FVC (L)	3.77±0.82	3.80±0.82	3.53±0.83	<0.001	3.62±0.82	3.58±0.80	0.659
FEV1/FVC	79.4±6.1	79.5±6.0	78.8±6.7	0.022	79.3±6.4	78.8±6.8	0.297

Notes: Data are presented as number (%) or the mean ± standard deviation.

a White collar job includes administrators, experts, and office workers.

b Blue collar job includes annual workers such as farmers, fishermen, and other manual workers.

c Single condition includes divorced, separated, or never married subjects.

Abbreviations: BDI, Beck Depression Inventory; BMI, body mass index; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 2 Mean and mean differences in FEV₁, FVC, and FEV₁/FVC (%) by the level of BDI score adjusted for other variables

Variable	Number	FEV1 (L)		P-value	FVC (L)		P-value	FEV1/FVC (%)		P-value
		Mean (SE)	Mean difference (SE)		Mean (SE)	Mean difference (SE)		Mean (SE)	Mean difference (SE)
Before propensity score matching (n=3,321)
BDI score				0.044			0.327			0.058
0–15	2,887	2.99 (0.01)	Reference		3.77 (0.01)	Reference		79.5 (0.1)	Reference
16–63	434	2.94 (0.02)	0.05 (0.02)		3.74 (0.25)	0.03 (0.02)		78.9 (0.2)	0.6 (0.2)
After propensity score matching (n=744)
BDI score				0.043			0.562			0.122
0–15	2,887	2.82 (0.02)	Reference		3.55 (0.01)	Reference		79.4 (0.1)	Reference
16–63	434	2.76 (0.02)	0.05 (0.03)		3.53 (0.25)	0.03 (0.02)		78.8 (0.2)	0.6 (0.4)

Notes: Data are presented as adjusted mean (SE) and mean difference (SE) unless otherwise indicated. FEV₁ and FVC were adjusted for age, sex, BMI, and smoking status. FEV₁/FVC (%) was not adjusted for age, sex, and smoking status.

Abbreviations: BDI, Beck Depression Inventory; BMI, body mass index; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; SE, standard error.

Table 3 Adjusted estimates of BDI for lung function according to multiple linear regression analysis

Dependent parameters	Before propensity score matching (n =3,321)			After propensity score matching (n =744)
	Estimated BDI score	Standard error	P-value	Estimated BDI score	Standard error	P-value
All
FEV1 (L)	−0.001	0.001	0.472	−0.002	0.001	0.107
FVC (L)	−0.001	0.001	0.732	−0.001	0.001	0.455
FEV1/FVC (%)	−0.009	0.014	0.844	−0.026	0.021	0.217
Age ≤50 years
FEV1 (L)	0.001	0.002	0.639	0.001	0.003	0.682
FVC (L)	0.001	0.002	0.476	0.003	0.003	0.298
FEV1/FVC (%)	−0.012	0.020	0.561	−0.031	0.033	0.341
Age >50 years
FEV1 (L)	−0.003	0.001	0.046	−0.005	0.002	0.022
FVC (L)	−0.003	−0.002	0.103	−0.004	0.002	0.150
FEV1/FVC (%)	−0.016	0.020	0.864	−0.032	0.029	0.273

Notes: Data are presented as adjusted mean (SE) and mean difference (SE) unless otherwise indicated. FEV₁ and FVC were adjusted for age, sex, BMI, and smoking status. FEV₁/FVC (%) was not adjusted for age, sex, and smoking status.

Abbreviations: BDI, Beck Depression Inventory; BMI, body mass index; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; SE, standard error.