Table 3.

Associations [aHR (95% CI)] of ${\mathrm{PM}}_{2.5}$ and ${\mathrm{NO}}_2$ with metabolic syndrome and its components among participants of the MJ Health Research cohort in Taiwan between 2006 and 2016.

MetS and its components	Model 1a		Model 2b		Model 3c
	${\mathrm{PM}}_{2.5}$	${\mathrm{NO}}_2$	${\mathrm{PM}}_{2.5}$	${\mathrm{NO}}_2$	${\mathrm{PM}}_{2.5}$	${\mathrm{NO}}_2$
Development of abdominal obesity in the no abdominal obesity cohort	($n=\mathrm{76,960}$; $e=\mathrm{8,555}$)		($n=\mathrm{70,729}$; $e=\mathrm{7,705}$)		($n=\mathrm{70,589}$; $e=\mathrm{7,698}$)
	1.15 (1.01, 1.12)	1.06 (0.99, 1.12)	1.08 (1.02, 1.15)	1.01 (0.95, 1.07)	1.07 (1.01, 1.14)	0.97 (0.92, 1.03)
Development of reduced HDL-C in the normal HDL-C cohort	($n=\mathrm{75,210}$; $e=\mathrm{12,542}$)		($n=\mathrm{68,733}$; $e=\mathrm{11,373}$)		($n=\mathrm{68,727}$; $e=\mathrm{11,372}$)
	1.16 (1.10, 1.22)	1.03 (0.99, 1.08)	1.17 (1.11, 1.23)	1.02 (0.97, 1.07)	1.17 (1.11, 1.23)	0.99 (0.94, 1.03)
Development of elevated TG in the normal TG cohort	($n=\mathrm{73,707}$; $e=\mathrm{7,210}$)		($n=\mathrm{67,592}$; $e=\mathrm{6,490}$)		($n=\mathrm{67,587}$; $e=\mathrm{6,489}$)
	1.10 (1.02, 1.18)	1.01 (0.95, 1.07)	1.12 (1.04, 1.20)	1.00 (0.94, 1.07)	1.09 (1.02, 1.17)	0.94 (0.88, 1.01)
Development of elevated BP in the normal BP cohort	($n=\mathrm{69,075}$; $e=\mathrm{12,965}$)		($n=\mathrm{63,514}$; $e=\mathrm{11,772}$)		($n=\mathrm{63,510}$; $e=\mathrm{11,771}$)
	1.18 (1.12, 1.24)	1.03 (0.98, 1.08)	1.18 (1.12, 1.24)	1.01 (0.97, 1.06)	1.15 (1.09, 1.21)	1.04 (0.99, 1.10)
Development of elevated FBG in the normal FBG cohort	($n=\mathrm{59,681}$; $e=\mathrm{20,549}$)		($n=\mathrm{54,274}$; $e=\mathrm{18,615}$)		($n=\mathrm{54,269}$; $e=\mathrm{18,614}$)
	1.11 (1.06, 1.15)	1.07 (1.03, 1.11)	1.11 (1.06, 1.16)	1.06 (1.02, 1.10)	1.15 (1.10, 1.20)	1.03 (0.99, 1.07)
Development of MetS based on the number of MetS components exhibited at baseline	($n=\mathrm{75,596}$; $e=\mathrm{9,818}$)		($n=\mathrm{69,460}$; $e=\mathrm{8,850}$)		($n=\mathrm{69,456}$; $e=\mathrm{8,848}$)
0	($n=\mathrm{34,285}$; $e=897$)		($n=\mathrm{31,788}$; $e=824$)		($n=\mathrm{31,787}$; $e=824$)
	0.99 (0.89, 1.11)	0.87 (0.75, 1.01)	0.99 (0.89, 1.11)	0.87 (0.75, 1.01)	0.99 (0.89, 1.12)	0.88 (0.76, 1.03)
1	($n=\mathrm{25,277}$; $e=\mathrm{3,175}$)		($n=\mathrm{23,137}$; $e=\mathrm{2,858}$)		($n=\mathrm{23,134}$; $e=\mathrm{2,856}$)
	1.12 (1.04, 1.20)	1.02 (0.94, 1.11)	1.12 (1.04, 1.21)	1.02 (0.94, 1.11)	1.12 (1.04, 1.20)	1.01 (0.93, 1.10)
2	($n=\mathrm{16,034}$; $e=\mathrm{5,746}$)		($n=\mathrm{14,535}$; $e=\mathrm{5,168}$)		($n=\mathrm{14,535}$; $e=\mathrm{5,168}$)
	1.12 (1.05, 1.19)	1.13 (1.06, 1.21)	1.12 (1.05, 1.19)	1.14 (1.06, 1.21)	1.14 (1.07, 1.22)	1.10 (1.03, 1.18)

Note: All estimates were calculated for every $10\text{-}{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ increase in ${\mathrm{PM}}_{2.5}$ and every $10\text{-ppb}$ increase in ${\mathrm{NO}}_2$ in the annual average concentrations, two-pollutant model, determined using time-dependent Cox regression. Missing information on covariates were initially represented by the previous value available of each participant. Participants without available value for representation were not eligible for data analysis depending on the covariates in the models, leading to different eligible numbers of participants in different models. The terms elevated and reduced refer to above and below normal reference range, respectively. aHR, adjusted hazard ratio; CI, confidence interval; BP, blood pressure; $e$, number of participants with the incident outcome; FBG, fasting blood glucose; HDL-C, high-density lipoprotein cholesterol; MetS, metabolic syndrome; $n$, number of participants without missing variables in each model; ${\mathrm{NO}}_2$, nitrogen dioxide; ${\mathrm{PM}}_{2.5}$, fine particulate matter (PM with an aerodynamic diameter of $\le 2.5\mathrm{\mu }\mathrm{m}$); TG, triglyceride.

^a Adjusted by age, sex, marital status (single/divorced/separation/widowed, married/cohabitating), education level (junior high school and below, general and vocational high school, college, master’s degree and above), smoking habits (never smoking/former smoking, secondhand smoke exposure, frequent smoking/daily smoking), alcohol drinking habits (never drinking/former drinking, occasional drinking, frequent drinking/daily drinking), sleeping time per day ($<6$, 6–8, $>8\mathrm{h}$), fried food consumption (none, little or $\le 1$ portion weekly, 2–3 portions weekly, $\ge 4$ portions weekly), processed food consumption (none, little or $\le 1$ portion weekly, 2–3 portions weekly, $\ge 4$ portions weekly), and region (north, central, south).

^b Additionally adjusted for the covariates from Model 1 and exercise (none, little or $<1\mathrm{h}$ weekly, 1–4 h weekly or once per 2–3 d; $\ge 5\mathrm{h}$ weekly or daily).

^c Additionally adjusted for the covariates from Model 2, baseline body mass index ($<18.5$, 18.5–24, $\ge 24{\mathrm{kg}/\mathrm{m}}^2$), and the initial status—baseline waist circumference for abdominal obesity cohort, baseline TG for elevated TG cohort, baseline HDL-C for reduced HDL-C cohort, baseline systolic BP and baseline diastolic BP for elevated BP cohort, baseline FBG for elevated FBG cohort.