Table 4.

Path analysis for the associations between education, occupation, FAI, and pulmonary function test indexes.

Independent variables	Dependent variables	β values of direct effects	β values of indirect effects	β values of total effects
Education	BMI	0.001	–	0.001
	Cigarette smoking	0.029	–	0.029
	Indoor air pollution	−0.139	–	−0.139
	Outdoor air pollution	−0.123	–	−0.123
	FEV1/FVC	0.113	−0.001	0.112
	FEV1	0.284	0.010	0.294
	FVC	0.249	0.011	0.260
	FEV1% pred	−0.076	−0.018	−0.094
Occupation	BMI	0.045	–	0.045
	Cigarette smoking	0.069	–	0.069
	Indoor air pollution	−0.183	–	−0.183
	Outdoor air pollution	0.122	–	0.122
	FEV1/FVC	−0.042	−0.009	−0.051
	FEV1	−0.102	0.033	−0.069
	FVC	−0.092	0.038	−0.054
	FEV1% pred	0.029	−0.001	0.028
Family average income	BMI	0.017	–	0.017
	Cigarette smoking	−0.060	–	−0.060
	Indoor air pollution	−0.117	–	−0.117
	Outdoor air pollution	−0.251	–	−0.251
	FEV1/FVC	0.043	0.025	0.068
	FEV1	0.066	−0.025	0.041
	FVC	0.049	−0.037	0.012
	FEV1% pred	−0.028	−0.013	−0.041

Data were shown as β values with statistical significance. All the β values in this table were adjusted for age, gender, residence, and parental history of respiratory diseases. BMI: Body mass index; FAI: Family average income; FEV₁: Forced expiratory volume in 1 s; FEV₁% pred: FEV₁ percentage of predicted; FVC: Forced vital capacity; –: Not applicable.