Table 1.

Characteristics of the study participants by measurement cycle, overall and by quartile of annual average ${\text{NO}}_2$ exposure ($N=\mathrm{1,762}$ participants).

Covariate	Overall	Quartile of annual average ${\text{NO}}_2$ exposure (concentration range ${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)				p-Valuea
		First (11.3–18.3)	Second (18.3–22.1)	Third (22.1–27.3)	Fourth (27.1–59.6)
Number of participants	1,762b	440	441	440	441
Age at baselinec (y) ($\text{mean}\pm \text{SD}$)	$75.5\pm 8.5$	$75.0\pm 8.1$	$74.7\pm 8.1$	$76.2\pm 8.7$	$76.3\pm 8.8$	0.0059
Female sex [n (%)]	970 (55.1)	54.1	52.2	58.2	55.8	0.3211
Educational leveld [n (%)]						$<0.0001$
Low	854 (48.5)	58.4	47.8	46.8	40.8
Medium	592 (33.6)	25.9	33.6	36.8	38.1
High	316 (17.9)	15.7	18.6	16.4	21.1
Smoking [n (%)]						0.1919
Never smoker	548 (31.1)	33.4	32.9	31.1	27.0
Ex-smoker	911 (51.7)	51.1	51.7	51.8	52.2
Current smoker	303 (17.2)	15.5	15.4	17.0	20.9
Alcohol consumptione [n (%)]						0.0854
Nondrinker	285 (16.2)	18.2	14.5	18.6	13.4
Light drinker	909 (51.6)	50.2	53.7	51.8	50.6
Moderate drinker	467 (26.5)	27.5	27.0	22.7	28.8
Excessive drinker	101 (5.7)	4.1	4.8	6.8	7.3
Physical activity past 2 wk [n (%)]						0.3181
$<78\text{min}/\mathrm{d}$	442 (25.1)	24.5	24.0	22.7	29.0
$78–199\text{min}/\mathrm{d}$	879 (49.9)	48.6	49.7	52.7	48.5
$\ge 199\text{min}/\mathrm{d}$	441 (25.0)	26.8	26.3	24.5	22.4
Depression [n (%)]	258 (14.6)	12.3	12.2	15.2	18.8	0.0163
Chronic diseases [n (%)]
Lung disease	227 (12.9)	11.1	12.2	15.5	12.7	0.2656
Cardiac disease	438 (24.9)	24.1	24.5	23.6	27.2	0.6086
Peripheral arteriosclerosis	133 (7.5)	6.1	7.0	7.7	9.3	0.3367
Diabetes	205 (11.6)	9.1	14.1	10.5	12.9	0.0858
Stroke	106 (6.0)	4.5	5.9	6.6	7.0	0.4314
Arthritis	829 (47.0)	44.5	43.1	50.2	50.3	0.0553
Cancer	247 (14.0)	14.3	12.2	14.1	15.4	0.5926
No. of above chronic diseases [n (%)]						0.0696
0	488 (27.7)	30.1	29.5	28.2	22.2
1	644 (36.5)	37.0	35.6	34.3	39.2
$\ge 2$	630 (35.8)	32.0	34.9	37.5	38.5
Changed addressf [n (%)]	473 (26.8)	26.5	29.3	25.0	26.8	0.5485
Status score of 4-digit postal code areag ($\text{mean}\pm \text{SD}$)	$0.03\pm 0.91$	$0.41\pm 0.42$	$0.37\pm 0.43$	$0.05\pm 0.78$	$-0.70\pm 1.24$	0.0059
Physical performance
Performance-based ($\text{mean}\pm \text{SD}$)	$10.8\pm 3.7$	$10.5\pm 3.9$	$10.3\pm 3.9$	$10.1\pm 3.9$	$9.3\pm 3.9$	$<0.001$
Self-reported ($\text{mean}\pm \text{SD}$)	$31.8\pm 5.1$	$30.9\pm 6.3$	$31.3\pm 5.7$	$30.1\pm 6.1$	$30.6\pm 5.9$	0.0298

^aF-test for age, status score, and physical performance, and chi-square test otherwise.

^bNumber of participants with estimated air pollution exposure, data on all potential confounders listed in Table 1, and performance-based and/or self-reported physical functioning for at least one measurement cycle.

^cAt the 2005/2006 measurement cycle.

^dLow: elementary not completed, elementary education, or lower vocational education; medium: general intermediate education, general intermediate education, or general secondary education; high: higher vocational education, college education, or university education.

^eLight: less than 1 d/mo, 1–3 d/mo and $<6$ consumption each time, 1–2 d/wk and $<4$ consumptions each time, $\ge 3$ days/week and less than 2 consumptions each time; moderate: 1–3 d/mo and $\ge 6$ consumptions each time, 1–2 d/wk and 4–5 consumptions each time, 3–4 d/wk and 2–4 consumptions each time, or 5–7 d/wk and 2–3 consumptions each time; excessive: 1–4 d/wk and $\ge 6$ consumptions each or 5–7 d/wk and $\ge 4$ consumptions each.

^fChange of address between 3 y prior to the 2005/2006 cycle and the last completed cycle.

^gMeasure of area-level socioeconomic status based on the average income, percentage of low income residents, percentage of residents with low level of education, and percentage of unemployed persons. Higher scores indicate a higher socioeconomic status.