Table 4.

Associations of air pollutants (per IQR increase) and air pollution index with the PHQ-4 Score and odds of mental disorders for 398,241 participants at baseline.

	PHQ-4 Score			Mental disordersa				Depression				Anxiety
Air pollutants	Coefficients (SE)	$p$-Value	E-value (CI)	$n_{\text{c}\text{a}\text{s}\text{e}}/n_{\text{t}\text{o}\text{t}\text{a}\text{l}}$	OR (95% CI)	$p$-Value	E-Value (CI)	$n_{\text{c}\text{a}\text{s}\text{e}}/n_{\text{t}\text{o}\text{t}\text{a}\text{l}}$	OR (95% CI)	p-value	E-value (CI)	${\text{N}}_{\text{c}\text{a}\text{s}\text{e}}/{\text{N}}_{\text{t}\text{o}\text{t}\text{a}\text{l}}$	Odds ratio (95% CI)	p-value	E-value (CI)
${\mathrm{PM}}_{2.5}$	0.051 (0.005)	$<0.0001$	1.17 (1.15)	52,365/398,241	1.07 (1.06, 1.09)	$<0.0001$	1.34 (1.31)	25,715/398,241	1.08 (1.07, 1.10)	$<0.0001$	1.37 (1.34)	41,783/398,241	1.07 (1.05–1.08)	$<0.0001$	1.34 (1.28)
${\mathrm{PM}}_{\text{coarse}}$	0.008 (0.003)	$<0.0001$	1.06 (1.03)	52,365/398,241	1.01 (1.00, 1.02)	0.18	1.11 (1.00)	25,715/398,241	1.02 (1.00, 1.03)	0.018	1.16 (1.00)	41,783/398,241	1.00 (0.99–1.01)	0.56	1.00 (1.00)
${\mathrm{PM}}_{10}$	0.034 (0.004)	$<0.0001$	1.14 (1.12)	52,365/398,241	1.03 (1.01, 1.04)	$<0.0001$	1.21 (1.11)	25,715/398,241	1.05 (1.03, 1.07)	$<0.0001$	1.28 (1.21)	41,783/398,241	1.02 (1.00–1.03)	0.010	1.16 (1.00)
${\mathrm{NO}}_{\mathrm{x}}$	0.046 (0.004)	$<0.0001$	1.16 (1.15)	52,365/398,241	1.05 (1.04, 1.06)	$<0.0001$	1.28 (1.24)	25,715/398,241	1.06 (1.05, 1.08)	$<0.0001$	1.31 (1.28)	41,783/398,241	1.04 (1.03–1.06)	$<0.0001$	1.24 (1.21)
${\mathrm{NO}}_2$	0.044 (0.004)	$<0.0001$	1.16 (1.14)	52,365/398,241	1.05 (1.03, 1.06)	$<0.0001$	1.28 (1.21)	25,715/398,241	1.08 (1.06, 1.09)	$<0.0001$	1.37 (1.31)	41,783/398,241	1.03 (1.02–1.05)	$<0.0001$	1.21 (1.16)

Air pollution indexb	Coefficients (SE)	$p$-Value	E-value (CI)	$n_{\text{case}}/n_{\text{total}}$	OR (95% CI)	$p$-Value	E-value (CI)	$n_{\text{case}}/n_{\text{total}}$	OR (95% CI)	p-value	E-value (CI)	${\text{N}}_{\text{c}\text{a}\text{s}\text{e}}/{\text{N}}_{\text{t}\text{o}\text{t}\text{a}\text{l}}$	Odds ratio (95% CI)	p-value	E-value (CI)
Continuous	0.046 (0.004)	$<0.0001$	1.16 (1.15)	52,365/398,241	1.05 (1.04, 1.06)	$<0.0001$	1.28 (1.24)	25,715/398,241	1.07 (1.06, 1.09)	$<0.0001$	1.34 (1.31)	41,783/398,241	1.05 (1.04–1.06)	$<0.0001$	1.28 (1.24)
Q1	Ref	—	—	8,098/79,649	Ref	—	—	3,581/79,649	Ref	—	—	6,492/79,649	Ref	—	—
Q2	0.024 (0.010)	0.024	1.10 (1.05)	9,188/79,647	1.04 (1.00, 1.08)	0.034	1.24 (1.00)	4,221/79,647	1.04 (0.99, 1.09)	0.12	1.24 (1.00)	7,392/79,647	1.04 (1.00–1.08)	0.042	1.24 (1.00)
Q3	0.067 (0.011)	$<0.0001$	1.20 (1.16)	10,335/79,648	1.11 (1.07, 1.14)	$<0.0001$	1.46 (1.34)	4,981/79,648	1.14 (1.09, 1.20)	$<0.0001$	1.54 (1.40)	8,253/79,648	1.09 (1.05–1.13)	$<0.0001$	1.40 (1.28)
Q4	0.089 (0.011)	$<0.0001$	1.24 (1.20)	11,584/79,649	1.15 (1.11, 1.19)	$<0.0001$	1.57 (1.46)	5,829/79,649	1.19 (1.13, 1.25)	$<0.0001$	1.67 (1.51)	9,249/79,649	1.13 (1.09–1.18)	$<0.0001$	1.61 (1.40)
Q5	0.127 (0.011)	$<0.0001$	1.30 (1.27)	13,160/79,648	1.16 (1.12, 1.20)	$<0.0001$	1.59 (1.49)	7,103/79,648	1.24 (1.18, 1.30)	$<0.0001$	1.79 (1.64)	10,397/79,648	1.14 (1.10–1.19)	$<0.0001$	1.54 (1.43)

Note: Associations of air pollution with PHQ-4 score were tested with mixed-effect linear regression models and associations with the odds of mental disorders, depression, and anxiety at baseline were tested with logistic regression models. Model adjusted for age, sex, BMI, race (White, Black, Asian, and other), smoking status (current/former/never), healthy alcohol intake status (male: $<28\mathrm{g}/\text{day}$; female: $<14\mathrm{g}/\text{day}$), healthy physical activity status [$\ge 150\text{\hspace{0.17em}min}/\mathrm{wk}$ moderate or $\ge 75\text{\hspace{0.17em}min}/\mathrm{wk}$ vigorous or 150 min/week mixed ($\text{moderate}\hspace{0.17em}+\hspace{0.17em}\text{vigorous}$) activity], years of education ($<10\mathrm{y}$), ${\text{FEV}}_1$, FVC, Townsend deprivation index, live in urban area (yes/no), and prevalent hypertension, CHD, and diabetes (yes/no). The examination center was controlled for as a random effect. Estimates were reported by one IQR increase in each air pollutant. IQRs of ${\mathrm{PM}}_{2.5}=1.27\mathrm{\mu }\mathrm{g}/\mathrm{m}³$, ${\mathrm{PM}}_{\text{coarse}}=0.79\mathrm{\mu }\mathrm{g}/\mathrm{m}³$, ${\mathrm{PM}}_{10}=2.33\mathrm{\mu }\mathrm{g}/\mathrm{m}³$, ${\mathrm{NO}}_{\mathrm{x}}=16.53\mathrm{\mu }\mathrm{g}/\mathrm{m}³$, ${\mathrm{NO}}_2=10.87\mathrm{\mu }\mathrm{g}/\mathrm{m}³$. —, no data; BMI, body mass index; CHD, coronary heart disease; CI, confidence interval; ${\text{FEV}}_1$ FVC, forced vital capacity; IQR, interquartile range; ${\mathrm{NO}}_2$, nitrogen dioxide; ${\mathrm{NO}}_{\mathrm{x}}$, nitrogen oxides; OR, odds ratio; PHQ-4, Patient Health Questionnaire-4 questionnaire; ${\mathrm{PM}}_{2.5}$, particulate matter with diameters $\le 2.5\mathrm{\mu }\mathrm{m}$; ${\mathrm{PM}}_{\text{coarse}}$, particulate matter with diameters $2.5–10\mathrm{\mu }\mathrm{m}$; ${\mathrm{PM}}_{10}$, particulate matter diameter of $\le 10\mathrm{\mu }\mathrm{m}$; Q1–Q5, first to fifth quintiles; Ref, reference; SE, standard error.

^a Mental disorders, with depression and/or anxiety, based on PHQ-4 questionnaires and hospital records.

^b To estimate the joint effect of multiple air pollutants on each outcome, an air pollution index was estimated using the coefficients of ${\mathrm{PM}}_{2.5}$, ${\mathrm{PM}}_{\text{coarse}}$, ${\mathrm{PM}}_{10}$, ${\mathrm{NO}}_{\mathrm{x}}$, and ${\mathrm{NO}}_2$ for the odds of mental disorders retrieved from the crude logistic model which adjusted for age and sex only.