Table 3.

Associations between childhood autism and green space metrics in elementary school districts stratified by road density examined with spatial regression models.

Explanatory variables (unit)	High road density (Q4)			Low road density (Q1)
	RR^a	95% CI	p	RR^a	95% CI	p
Urban land (10%)	1.10	1.06 – 1.15	<0.001	1.22^b	1.01^b – 1.74^b	0.040
Forest (10%)	0.87	0.78 – 0.96	<0.001	1.03	0.96 – 1.11	0.421
Grassland (10%)	0.94	0.85 – 1.05	0.259	0.95	0.87– 1.04	0.233
Average tree canopy (10%)	0.86	0.79 – 0.93	<0.001	1.01	0.92 – 1.10	0.843
Near–road tree canopy, 50 m, (10%)	0.79	0.71 – 0.87	<0.001	1.05	0.95 – 1.17	0.307

^a:

adjusted for economic status (median household income), race (proportion of white population) and gender (proportion of male population).

^b:

the RR value is corresponding to the 1% change of urban land.