Table 1.

Background characteristics related to asthma in a Swedish cohort of 2 775 430 individuals

	No asthma	Asthma
n (%)	2 514 108 (90.6)	261 322 (9.4)
Study individuals’ characteristics
Sex
Male	1 277 846 (50.9)	147 383 (56.4)
Female	1 236 255 (49.2)	113 939 (43.6)
Prematurity
Yes (≤37 weeks)	144 043 (5.7)	22 243 (8.5)
No (>37 weeks)	2 382 811 (94.3)	239 079 (91.5)
Small for gestational age
Yes	56 886 (2.2)	7145 (2.7)
No	2 382 811 (94.8)	245 453 (94.0)
Missing	74 411 (3.0)	8724 (3.3)
Life-limiting condition
Yes	28 798 (1.1)	6480 (2.5)
No	2 485 310 (98.9)	254 842 (97.5)
Family characteristics
Maternal age at delivery, years
<20	52 249 (2.1)	5444 (2.1)
≥20 to <25	420 197 (16.7)	45 615 (17.4)
≥25 to <30	840 276 (33.4)	90 611 (34.6)
≥30 to <35	779 249 (31.0)	79 073 (30.3)
≥35 to <40	349 137 (13.8)	33 960 (13.0)
≥40	71 630 (2.9)	6486 (2.5)
Missing	1370 (0.1)	133 (0.1)
Maternal smoking during pregnancy
Yes	356 193 (14.2)	39 347 (15.1)
No	2 016 479 (80.2)	206 644 (79.1)
Missing	141 436 (5.6)	15 331 (5.8)
Maternal country of birth
Sweden	2 066 737 (82.2)	225 482 (86.3)
Denmark, Norway, Finland, Iceland	69 516 (2.8)	6600 (2.5)
Other	374 597 (14.9)	29 214 (11.2)
Missing	3258 (0.1)	26 (<0.1)
Parental income
Lowest	486 986 (19.4)	46 634 (17.9)
Lower middle	481 091 (19.1)	51 179 (19.6)
Middle	480 864 (19.1)	51 918 (19.9)
Upper middle	480 520 (19.1)	51 276 (19.6)
Highest	483 183 (19.2)	48 684 (18.6)
Missing	101 464 (4.0)	11 631 (4.5)
Parental education
Compulsory school	161 801 (6.4)	15 364 (5.9)
High school	1 132 088 (45.1)	125 046 (47.8)
College or further education	1 101 778 (43.8)	108 189 (41.4)
Missing	118 441 (4.7)	12 723 (4.9)

The table compares those who received a diagnosis of asthma during follow-up with those who did not receive a diagnosis of asthma during follow-up.