Table 1.

Age-standardized characteristics of Nurses’ Health Study participants throughout follow-up (1988–2008), overall, by quintile of 24-month average ambient ${\mathrm{PM}}_{2.5}$ exposure, and by quartile of total physical activity ($N=\mathrm{104,990}$).

	$\text{Mean}\pm \text{SD}$ or %a
		${\mathrm{PM}}_{2.5}$	${\mathrm{PM}}_{2.5}$	Physical activity	Physical activity
Characteristicb	Overall	Quintile 1	Quintile 5	Quartile 1	Quartile 4
Age (y)c	$63.1\pm 8.9$	$66.6\pm 8.3$	$58.7\pm 8.2$	$63.7\pm 9.3$	$63.0\pm 8.4$
24-month average ambient ${\mathrm{PM}}_{2.5}\left({\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3\right)$	$13.7\pm 3.5$	$9.1\pm 1.3$	$18.8\pm 2.0$	$13.9\pm 3.5$	$13.4\pm 3.5$
Physical activity (MET-h/wk)
Overall physical activity	$18.3\pm 23.1$	$20.3\pm 24.8$	$16.8\pm 21.3$	$1.5\pm 1.1$	$47.6\pm 28.9$
Walking	$7.2\pm 10.6$	$7.2\pm 9.7$	$8.0\pm 12.4$	$1.4\pm 4.3$	$15.5\pm 14.8$
Jogging	$0.3\pm 2.7$	$0.3\pm 2.7$	$0.2\pm 2.7$	$0.0\pm 0.6$	$0.9\pm 5.1$
Running	$0.2\pm 3.6$	$0.3\pm 4.0$	$0.2\pm 3.3$	$0.0\pm 0.7$	$0.8\pm 7.0$
Biking	$1.9\pm 6.4$	$2.0\pm 6.6$	$1.9\pm 6.5$	$0.1\pm 1.3$	$4.9\pm 11.2$
Vigorous activity	$3.8\pm 11.6$	$4.2\pm 12.3$	$3.6\pm 11.3$	$0.2\pm 2.8$	$11.0\pm 20.3$
Outdoor physical activityd	$17.8\pm 22.4$	$19.5\pm 23.8$	$16.6\pm 21.1$	$1.5\pm 1.1$	$46.1\pm 28.2$
Pack-years of smoking	$13.1\pm 19.5$	$12.7\pm 19.0$	$13.2\pm 19.9$	$16.1\pm 22.5$	$11.4\pm 17.3$
Census tract median income (per 1,000 USD)	$64.0\pm 25.0$	$60.4\pm 23.9$	$61.9\pm 24.3$	$62.2\pm 23.5$	$66.0\pm 26.9$
Census tract median home value (per 1,000 USD)	$172.3\pm 128.9$	$174.8\pm 142.6$	$169.5\pm 129.7$	$161.8\pm 114.5$	$185.2\pm 144.5$
Race and ethnicity
White	94	95	92	93	94
Black	1	1	2	2	1
Other/more than one race	5	4	6	5	5
Hispanic	1	2	1	1	1
24-month average ${\mathrm{PM}}_{2.5}$ quintiles (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)
Quintile 1: $<10.7$	20	100	0	18	23
Quintile 2: 10.7 to $<12.5$	20	0	0	20	20
Quintile 3: 12.5 to $<14.4$	20	0	0	20	20
Quintile 4: 14.4 to $<16.5$	20	0	0	21	19
Quintile 5: $\ge 16.5$	20	0	100	21	18
Total physical activity quartiles (MET-h/wk)
Quartile 1: $<3.7$	25	23	27	100	0
Quartile 2: 3.7 to $<10.9$	25	23	26	0	0
Quartile 3: 10.9 to $<24.4$	25	25	25	0	0
Quartile 4: $\ge 24.4$	25	28	22	0	100
Any vigorous physical activity reported	33	35	33	12	54
Body mass index (${\mathrm{kg}/\mathrm{m}}^2$)
$<25$	47	48	50	38	57
25 to $<30$	33	32	32	32	30
$\ge 30$	20	20	19	30	12
High blood pressure	43	44	41	49	38
High cholesterol	53	55	47	54	50
Diabetes	7	7	7	11	5
Family history of myocardial infarction	37	35	39	38	37
Smoking status
Never smoker	44	44	47	42	44
Past smoker	43	46	39	41	46
Current smoker	12	10	14	16	9
Alcohol consumption (grams/day)
0	55	54	58	63	50
0.1 to $<5$	23	21	23	20	23
5 to $<15$	14	15	12	11	17
15 to $<30$	5	6	4	4	6
$\ge 30$	3	4	3	3	3
AHEI diet score quartile
Quartile 1: $<42.9$	25	22	28	35	18
Quartile 2: 42.9 to $<51.8$	25	23	25	28	21
Quartile 3: 51.8 to $<60.4$	25	25	24	22	26
Quartile 4: $\ge 60.4$	25	30	22	15	36
Multivitamin use	47	50	41	42	51
Mother’s occupation housewife	64	62	68	64	64
Father’s occupation professional/manager	26	28	24	24	28
Husband’s highest level of education more than high school	42	44	41	37	48
Registered nursing degree in 1972	86	85	88	85	87
Married - ever	75	76	73	73	76
Retired - ever	44	46	41	42	46

Note: AHEI, Alternate Healthy Eating Index; MET, metabolic equivalent of task; ${\mathrm{PM}}_{2.5}$, particulate matter $<2.5\text{\hspace{0.17em}microns}$; SD, standard deviation.

^aValues are $\text{means}\pm \text{SD}$ or percentages and are standardized to the age distribution of the study population and represent the average values over the course of follow-up from 1988 to 2008, accounting for changes in time-varying characteristics.

^bCharacteristics are updated every 2 y, with the exception of diet, which is queried every 4 y, race (assessed in 2004), family history of MI (assessed in 1984), occupation of the participant’s father and mother (assessed in 1976), educational attainment of the participant’s husband (assessed in 1992), and participant’s educational attainment (assessed in 1992).

^cNot age standardized.

^dOutdoor physical activity excludes types of assessed physical activity that are more likely to be engaged in indoors for some or all of the time (squash, racquet ball, arm weight training, leg weight training).