Table 4.

Subgroup analyses of the effect of ambient NO₂ on the RR of HA-AKI

Variable	Subgroup	n	RR (95% CI)a	P for interaction
Age (years)	≤60	5118	1.082 (1.036–1.130)	–
	>60	6175	1.054 (1.010–1.099)	0.29
Gender	Male	7624	1.052 (1.012–1.095)	–
	Female	3669	1.098 (1.044–1.154)	0.11
Baseline eGFR (mL/min/1.73 m2)	≤60	8137	1.068 (1.027–1.110)	–
	>60	3156	1.066 (1.011–1.123)	0.95
AKI severity	Mild	8118	1.061 (1.021–1.103)	–
	Severe	3175	1.082 (1.026–1.141)	0.50
Intensive care	Yes	3653	1.081 (1.030–1.135)	–
	No	7640	1.058 (1.016–1.102)	0.42
Season	Q1	2784	1.085 (1.032–1.141)	–
	Q2	2882	1.096 (1.027–1.169)	0.80
	Q3	2758	1.037 (0.959–1.121)	0.31
	Q4	2869	1.045 (0.992–1.100)	0.22

^aRRs (95% CIs) were scaled by 1 MAD of the daily concentration of NO₂.