Table 1.

Descriptive statistics at the cohort baseline in 1993 or 1999 for 23,528 Danish Nurse Cohort study participants by AF incidence status at the end of follow-up on 31 July 2015.

	Total $n=\mathrm{23,528}$	AF $n=\mathrm{1,522}$	No AF $n=\mathrm{22,006}$
Cohort year or entry [$n$ (%)]
1993	15,035 (63.9)	1,264 (83.0)	13,771 (62.6)
1999	8,493 (36.1)	258 (17.0)	8,253 (37.4)
Age, $\text{mean}\pm \text{SD}$	$52.6\pm 7.7$	$57.0\pm 8.6$	$52.3\pm 7.5$
Body mass index (${\mathrm{kg}/\mathrm{m}}^2$), $\text{mean}\pm \text{SD}$	$23.7\pm 3.5$	$24.5\pm 4.0$	$23.6\pm 3.5$
Body mass index (${\mathrm{kg}/\mathrm{m}}^2$) [$n$ (%)]
Underweight ($<18.5{\mathrm{kg}/\mathrm{m}}^2$)	576 (2.5)	37 (2.5)	539 (2.5)
Normal weight ($18.5-25{\mathrm{kg}/\mathrm{m}}^2$)	16,137 (69.3)	907 (60.6)	15,230 (69.9)
Overweight ($25-30{\mathrm{kg}/\mathrm{m}}^2$)	5,271 (22.6)	411 (27.5)	4,860 (22.3)
Obese ($\ge 30{\mathrm{kg}/\mathrm{m}}^2$)	1,301 (5.6)	141 (9.4)	1,160 (5.3)
Missing (n)	358	40	318
Smoking status [$n$ (%)]
Never	8,166 (34.7)	464 (30.5)	7,702 (35.0)
Previous	7,145 (30.4)	489 (32.1)	6,656 (30.2)
Current	8,217 (34.9)	569 (37.4)	7,648 (34.8)
Missing ($n$)	962	84	878
Alcohol consumption [$n$ (%)]
None (0 drinks/wk)	3,579 (15.2)	279 (18.3)	3,300 (15.0)
Moderate (1–15 drinks/wk)	14,499 (61.6)	913 (60.0)	13,586 (61.7)
Heavy ($>15\text{\hspace{0.17em}drinks}/\mathrm{wk}$)	5,450 (23.2)	330 (21.7)	5,120 (23.3)
Missing (n)	861	77	784
Physical activitya [$n$ (%)]
Low	1,561 (6.6)	118 (7.8)	1,443 (6.6)
Medium	15,676 (66.6)	1,019 (67.0)	14,657 (66.6)
High	6,291 (26.7)	385 (25.3)	5,906 (26.8)
Missing ($n$)	356	32	324
Fruit consumption [$n$ (%)]
Rarely	864 (3.7)	58 (3.8)	806 (3.7)
Few times per week	6,724 (28.6)	402 (26.4)	6,322 (28.7)
Daily or several times per day	15,940 (67.7)	1,062 (69.8)	14,878 (67.6)
Missing ($n$)	454	50	404
Hypertension [$n$ (%)]
No	20,553 (87.5)	1,197 (78.8)	19,356 (88.1)
Yes	2,945 (12.5)	323 (21.2)	2,622 (11.9)
Missing ($n$)	44	3	41
Diabetesb [$n$ (%)]
No	23,066 (98.8)	1,486 (98.2)	21,580 (98.8)
Yes	284 (1.2)	27 (1.8)	257 (1.2)
Missing ($n$)	260	16	244
Myocardial infarctionb [$n$ (%)]
No	23,254 (99.3)	1,495 (98.7)	21,759 (99.4)
Yes	156 (0.7)	20 (1.3)	136 (0.6)
Missing ($n$)	189	13	176
Employment shift typec [$n$ (%)]
Day	11,683 (62.4)	602 (61.2)	11081 (62.5)
Evening	1,860 (9.9)	116 (11.8)	1,744 (9.8)
Night	1,019 (5.4)	71 (7.2)	948 (5.3)
Rotating	4,163 (22.2)	195 (19.8)	3,968 (22.4)
Missing ($n$)	7,290	835	6,455
Marital status [$n$ (%)]
Married	16,557 (70.4)	973 (63.9)	15,584 (70.8)
Separated	421 (1.8)	26 (1.7)	395 (1.8)
Divorced	2,786 (11.8)	181 (11.9)	2,605 (11.8)
Single	2,329 (9.9)	190 (12.5)	2,139 (9.7)
Widowed	1,435 (6.1)	152 (10.0)	1,283 (5.8)
Missing [$n$ (%)]	247	18	229
Hormone-replacement therapy [$n$ (%)]
Never	16,973 (73.3)	967 (64.5)	16,006 (73.9)
Previous	2,238 (9.7)	229 (15.3)	2,009 (9.3)
Current	3,945 (17.0)	303 (20.2)	3,642 (16.8)
Missing ($n$)	505	30	475
Urbanization level [$n$ (%)]
Rural	9,716 (41.3)	657 (43.2)	9,059 (41.2)
Provincial	10,262 (43.6)	631 (41.5)	9,631 (43.8)
Urban	3,550 (15.1)	234 (15.4)	3,316 (15.1)
Missing ($n$)	840	80	760
Annual air pollution exposure levels at cohort baseline
${\mathrm{PM}}_{2.5}$ levels (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$), $\text{mean}\pm \text{SD}$	$19.7\pm 3.6$	$20.7\pm 3.3$	$19.6\pm 3.6$
${\mathrm{PM}}_{2.5}$ levels (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$) [$n$ (%)]
Low ($<19.5$)	11,762 (50.0)	535 (35.2)	11,227 (51.0)
Medium (19.5–23.2)	8,343 (35.5)	668 (43.9)	7,675 (34.9)
High ($>23.2$)	3,423 (14.5)	319 (21.0)	3,104 (14.1)
Missing ($n$)	2,917	304	2,613
${\mathrm{NO}}_2$ levels (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$), $\text{mean}\pm \text{SD}$	$12.6\pm 8.1$	$13.2\pm 8.4$	$12.6\pm 8.1$
${\mathrm{NO}}_2$ levels (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$) [$n$ (%)]
Low ($<7.5$)	5,869 (24.9)	322 (21.2)	5,547 (25.5)
Medium (7.5-15.7)	11,833 (50.3)	766 (50.3)	11,067 (50.3)
High ($>15.7$)	5,826 (24.8)	434 (28.5)	5,392 (24.5)
Missing ($n$)	2,917	304	2,613
Annual road traffic noise exposure levels at cohort baseline
${\mathrm{L}}_{\text{den}}$ (dB), $\text{mean}\pm \text{SD}$	$52.7\pm 8.2$	$53.2\pm 7.8$	$52.7\pm 8.2$
${\mathrm{L}}_{\text{den}}$ (dB), $n$ (%)
Low ($<48$)	5,281 (22.4)	308 (20.2)	4,973 (22.6)
Medium (48–58)	12,316 (52.3)	800 (52.6)	11,516 (52.3)
High ($>58$)	5,931 (25.2)	414 (27.2)	5,517 (25.1)
Missing ($n$)	2,917	304	2,613

Note: Data are complete, unless otherwise indicated. “Missing” represents data that were excluded from analyses. AF, atrial fibrillation; dB, decibel; ${\mathrm{L}}_{\text{den}}$, annual mean 24-h road traffic noise levels; ${\mathrm{NO}}_2$, nitrogen dioxide; ${\mathrm{PM}}_{2.5}$, particulate matter with an aerodynamic diameter of $<2.5{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$; SD, standard deviation.

^aPhysical activity defined: low (typically reading or watching television in leisure time or doing other mainly sedentary leisure time activities)/medium (walking, biking, or other types of light physical activity at least 4 times a week, including weekend walks, light gardening, and cycling/walking to and from work)/high (exercising regularly/participation in organized sports and/or heavy gardening at least 4 times a week; high-intensity training or participating in professional sports at least 4 times a week).

^bSelf-reported (diagnosed/taking medication for).

^cAmong those actively employed at cohort entry ($n=\mathrm{18,725}$).