Table 1.

Descriptive statistics of full cohort ($N=\mathrm{13,590,387}$) and below-WHO guidelines cohort ($N=\mathrm{9,669,469}$) created from Medicare beneficiary denominator from 2000 to 2016 in seven southeastern U.S. states.

Categories	Full cohort		Below-WHO guidelines cohorta
	$N$	%	$N$	%
Full cohort
Deaths	4,898,015	36.0	2,814,617	29.1
Total population	13,590,387	100	9,669,469	100
Total person-years	107,291,652	100	69,077,046	100
Median follow-up year	8		7
Age at entry (y)
65–74	13,527,082	99.5	9,632,655	99.6
75–84	53,181	0.4	30,404	0.3
85–94	9,523	0.07	6,008	0.06
$\ge 95$	599	0.004	402	0.004
Sex
Male	5,943,391	43.7	4,321,795	44.7
Female	7,646,996	56.3	5,347,674	55.3
Race
White	11,217,509	82.5	8,073,062	83.5
Black	1,745,096	12.8	1,190,084	12.3
Otherb	627,782	4.6	406,323	4.2
Medicaid eligibility
Dual-eligible	1,718,169	12.6	1,154,668	11.9
Non–dual-eligible	11,872,218	87.4	8,514,801	88.1

Note: The seven states include Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Tennessee. WHO, World Health Organization.

^a The cohort was restricted to populations who were always exposed to annual mean ${\mathrm{NO}}_2$ levels below the current WHO guidelines, i.e. ${40\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$.

^b Other included Asian, Hispanic, American Indian or Alaskan Native, and unknown.