Background
Methods
Prevention of allergy among children in Trondheim study
Study design and participants
Outcome variables
Allergy-related condition | Time point(s) | Questions used to define cases |
---|---|---|
Asthma (ever) | 2 years | “Has the child ever been diagnosed with asthma by a doctor” |
Asthma (current) | 6 years | As asthma (ever) AND “Has the child been treated with tablets, inhalation medications or other treatments for wheezing, tightness in the chest or asthma during the last 12 months? |
Wheeze (ever) | 2 years | “Has the child ever had whistling in the chest?” AND “Has the child ever had episodes of wheezing or tightness in the chest? |
Wheeze (current) | 6 years | As for wheeze (ever) AND “Has the child had whistling, rattling or tightness in the chest in the past 12 months? |
ARC (ever) | 2 & 6 years | “Has the child ever had hay fever, sneezing or itchy-watery eyes? |
Eczema (ever) | 2 & 6 years | “Has the child ever had eczema?” AND “Has the child ever had an itchy rash which came and went over at least six months? |
Eczema (current) | 6 years | As for eczema (ever) AND “Has the child during the last 12 months used medications, balms, creams, tablets or herbal medicines for eczema? |
Exposure variables
Statistics
Results
Disease and age | N* | n | % | 95% CI |
---|---|---|---|---|
Asthma | ||||
2 years (ever) | 6101 | 403 | 6.6 | 6.0, 7.3 |
6 years (current) | 3705 | 175 | 4.7 | 4.1, 5.5 |
Wheeze | ||||
2 years (ever) | 5922 | 1577 | 26.6 | 25.5, 27.8 |
6 years (current) | 3668 | 388 | 10.6 | 9.6, 11.6 |
ARC | ||||
2 years (ever) | 5562 | 354 | 6.4 | 5.8, 7.0 |
6 years (ever) | 3438 | 424 | 12.3 | 11.3, 13.5 |
Eczema | ||||
2 years (ever) | 5927 | 998 | 16.8 | 15.9, 17.8 |
6 years (current) | 3648 | 505 | 13.8 | 12.8, 15.0 |
6 years (ever) | 3630 | 710 | 19.6 | 18.3, 20.9 |
Breastfeeding duration
Duration of any breastfeeding (N = 6796) | ||||
---|---|---|---|---|
≥ 6 months (n = 5695) | < 6 months (n = 1101) | |||
Characteristics | na | na | ||
Maternal age at birth, years, mean (SD) | 5670 | 30.2 (4.4) range: 16.8–44.5 | 1095 | 28.7 (5.1) range: 17.0–44.2 |
Maternal education, n (%) | 2625 | 392 | ||
< 12 years (less than high school) | 116 (4.4) | 62 (15.8) | ||
12–16 years (up to 4 years university) | 1298 (49.5) | 237 (60.5) | ||
> 16 years (more than 4 years university) | 1211 (46.1) | 93 (23.7) | ||
Mean incomeb, NOK, mean (SD) | 5465 | 255,414 (29175) | 1053 | 250,191 (30405) |
Family history of allergyc, n (%) | 5675 | 4200 (74.0) | 1092 | 784 (71.8) |
Older sibling, n (%) | 3943 | 2245 (56.9) | 731 | 401 (54.9) |
Maternal smoking, n (%) | ||||
During pregnancy | 2020 | 92 (4.6) | 316 | 55 (17.4) |
During child’s first 2 years | 5638 | 887 (15.7) | 1078 | 391 (36.3) |
Paternal smoking, n (%) | 5397 | 1072 (19.9) | 994 | 330 (33.2) |
Child exposed to smoke during first 2 yearsd, n (%) | 5675 | 1462 (25.8) | 1095 | 502 (45.8) |
Petse, n (%) | 5695 | 1143 (20.1) | 1101 | 264 (24.0) |
Birthweight, gram, mean (SD) | 5625 | 3608 (552) range: 640–5560 | 1072 | 3463 (705) range: 585–5960 |
Birthweight < 2500 g, n (%) | 5625 | 156 (2.8) | 1072 | 88 (8.2) |
Sex, male, n (%) | 5693 | 2798 (49.2) | 1101 | 581 (52.8) |
Lower respiratory tract infection within first yearf, n (%) | 3217 | 333 (10.4) | 606 | 78 (12.9) |
Antibiotic treatment within first year, n (%) | 3746 | 756 (20.2) | 695 | 163 (23.5) |
Introduced to formula < 6 months of age, n (%) | 5625 | 966 (17.2) | 1093 | 972 (88.9)g |
Start of day-care < 12 months of age, n (%) | 5051 | 394 (7.8) | 930 | 65 (7.0) |
Breastfeeding and allergy-related disease
Duration of any breastfeeding (N = 6796) | Odds ratioa (95% CI) | |||||
---|---|---|---|---|---|---|
≥ 6 months (n = 5695) | < 6 months (n = 1101) | |||||
Disease and age | nb | n (%) | nb | n (%) | Crude | Adjustedc |
Asthma | ||||||
2 years (ever) | 5135 | 319 (6.2) | 964 | 83 (8.6) | 0.70 (0.55, 0.90) | 0.77 (0.59, 1.02) |
6 years (current) | 3134 | 142 (4.5) | 566 | 32 (5.7) | 0.79 (0.53, 1.17) | 0.79 (0.51, 1.21) |
Wheeze | ||||||
2 years (ever) | 4981 | 1288 (25.9) | 939 | 288 (30.7) | 0.79 (0.68, 0.92) | 0.90 (0.76, 1.07) |
6 years (current) | 3098 | 312 (10.1) | 565 | 76 (13.5) | 0.72 (0.55, 0.94) | 0.71 (0.53, 0.95) |
ARC | ||||||
2 years (ever) | 4690 | 268 (5.7) | 871 | 86 (9.9) | 0.55 (0.43, 0.71) | 0.65 (0.49, 0.86) |
6 years (ever) | 2913 | 348 (12.0) | 520 | 76 (14.6) | 0.79 (0.61, 1.04) | 0.77 (0.58, 1.04) |
Eczema | ||||||
2 years (ever) | 4994 | 853 (17.1) | 931 | 145 (15.6) | 1.12 (0.92, 1.35) | 1.16 (0.94, 1.44) |
6 years (current) | 3087 | 436 (14.1) | 556 | 69 (12.4) | 1.16 (0.88, 1.52) | 1.15 (0.86, 1.55) |
6 years (ever) | 3071 | 613 (20.0) | 554 | 97 (17.5) | 1.17 (0.93, 1.49) | 1.18 (0.92, 1.53) |
Timing of introduction to complementary foods and allergy-related disease
Age at introduction of complementary foods (N = 3814) | ||||
---|---|---|---|---|
≥ 6 months (n = 996) | < 6 months (n = 2818) | |||
Characteristics | na | na | ||
Maternal age at birth, years, mean (SD) | 994 | 31.2 (4.2) range: 18.0–43.8 | 2810 | 29.6 (4.5) range: 17.0–43.7 |
Maternal education, n (%) | 596 | 1409 | ||
< 12 years (less than high school) | 17 (2.9) | 106 (7.5) | ||
12–16 years (up to 4 years university) | 288 (48.3) | 749 (53.2) | ||
> 16 years (more than 4 years university) | 291 (48.8) | 554 (39.3) | ||
Mean incomeb, NOK, mean (SD, range) | 952 | 256,368 (28674) | 2699 | 254,101 (29284) |
Family history of allergyc, n (%) | 995 | 768 (77.2) | 2812 | 2147 (76.4) |
Older sibling, n (%) | 995 | 588 (59.1) | 2809 | 1570 (55.9) |
Maternal smoking, n (%) | ||||
During pregnancy | 538 | 10 (1.9) | 1126 | 91 (8.1) |
During child’s first 2 years | 994 | 107 (10.8) | 2807 | 597 (21.3) |
Paternal smoking, n (%) | 981 | 170 (17.3) | 2717 | 680 (25.0) |
Child exposed to smoke during first 2 yearsd, n (%) | 995 | 201 (20.2) | 2817 | 923 (32.8) |
Petse, n (%) | 996 | 239 (24.0) | 2818 | 633 (22.5) |
Birthweight, gram, mean (SD, range) | 992 | 3583 (576) range: 1100–5500 | 2808 | 3587 (577) range: 585–5370 |
Birthweight < 2500 g, n (%) | 992 | 31 (3.1) | 2808 | 106 (3.8) |
Sex, male, n (%) | 996 | 465 (46.7) | 2818 | 1418 (50.3) |
Lower respiratory tract infection within first yearf, n (%) | 992 | 101 (10.2) | 2809 | 307 (10.1) |
Antibiotic treatment within first year, n (%) | 995 | 203 (20.4) | 2812 | 689 (24.5) |
Introduced to formula < 6 months of age, n (%) | 992 | 127 (12.8) | 2810 | 897 (31.9) |
Start of day-care < 12 months of age, n (%) | 806 | 70 (8.7) | 2281 | 200 (8.8) |
Introduction to complementary foods (N = 3814) | Odds ratioa (95% CI) | |||||
---|---|---|---|---|---|---|
≥ 6 months (n = 996) | < 6 months (n = 2818) | |||||
Disease and age | nb | n (%) | nb | n (%) | Crude | Adjustedc |
Asthma | ||||||
2 years (ever) | 818 | 46 (5.6) | 2328 | 143 (6.1) | 0.91 (0.65, 1.28) | 0.92 (0.64, 1.34) |
6 years (current) | 644 | 30 (4.7) | 1699 | 75 (4.4) | 1.06 (0.69, 1.63) | 1.18 (0.75, 1.86) |
Wheeze | ||||||
2 years (ever) | 797 | 173 (21.7) | 2256 | 582 (25.8) | 0.80 (0.66, 0.97) | 0.85 (0.70, 1.05) |
6 years (current) | 637 | 70 (11.0) | 1683 | 173 (10.3) | 1.08 (0.80, 1.45) | 1.13 (0.83, 1.54) |
ARC | ||||||
2 years (ever) | 757 | 36 (4.8) | 2127 | 133 (6.3) | 0.75 (0.51, 1.09) | 0.88 (0.60, 1.30) |
6 years (ever) | 603 | 76 (12.6) | 1591 | 203 (12.8) | 0.99 (0.74, 1.31) | 1.09 (0.81, 1.47) |
Eczema | ||||||
2 years (ever) | 793 | 118 (14.9) | 2267 | 360 (15.9) | 0.93 (0.74, 1.16) | 0.98 (0.77, 1.24) |
6 years (current) | 631 | 82 (13.0) | 1670 | 224 (13.4) | 0.96 (0.74, 1.26) | 0.96 (0.72, 1.28) |
6 years (ever) | 629 | 113 (18.0) | 1661 | 328 (19.8) | 0.89 (0.70, 1.13) | 0.89 (0.69, 1.13) |
Discussion
Main results
Condition & age | Comparison for breastfeeding durationa | All studies included | Prospective cohort studies | Ref | ||
---|---|---|---|---|---|---|
Nb | OR | N | OR | |||
Wheeze | ||||||
0–4 yo | TBF > 5-7mo vs. < 5-7mo | 9 | 0.90 (0.72, 1.12) | 6 | 0.89 (0.65, 1.21) | [6] |
5–14 yo | TBF > 5-7mo vs. < 5-7mo | 2 | 0.86 (0.70, 1.06) | 1 | 0.88 (0.71, 1.09) | [6] |
Recurrent wheeze | ||||||
0–4 yo | TBF > 5-7mo vs. < 5-7mo | 6 | 0.79 (0.61, 1.04) | 3 | 0.73 (0.56, 0.96) | [6] |
5–14 yo | TBF > 5-7mo vs. < 5-7mo | 9 | 0.76 (0.62, 0.92) | 4 | 0.82 (0.66, 1.03) | [6] |
Asthmac | ||||||
5–18 yo | More vs. Less | 29 | 0.90 (0.84, 0.97) | 13 | 0.94 (0.80, 1.11) | [7] |
Allergic rhinitis / rhinoconjunctivitis | ||||||
0–4 yo | TBF > 5-7mo vs. < 5-7mo | 2 | 0.81 (0.64, 1.02) | --- d | [6] | |
0–5 yo | More vs. Less | 6 | 0.79 (0.63, 0.98) | 2 | 0.91 (0.74, 1.13) | [7] |
5–14 yo | TBF > 5-7mo vs. < 5-7mo | 1 | 1.14 (0.75, 1.72) | --- d | [6] | |
5–18 yo | More vs. Less | 9 | 1.05 (0.99, 1.12) | 4 | 1.12 (1.02, 1.24) | [7] |
Ezcema | ||||||
0–2 yo | More vs. Less | 16 | 0.95 (0.85, 1.07) | 15 | 0.97 (0.86, 1.10) | [7] |
0–4 yo | TBF > 5-7mo vs. < 5-7mo | 4 | 0.93 (0.80, 1.07) | 3 | 0.97 (0.75, 1.12) | [6] |
2–18 yo | More vs. Less | 20 | 1.09 (0.99, 1.20) | 6 | 1.36 (0.90, 2.06) | [7] |
5–14 yo | TBF > 5-7mo vs. < 5-7mo | 2 | 1.35 (1.07, 1.72) | --- d | [6] |