Table 4.
Distribution of road exposures at birth and pooled road exposures by asthma status by age 5 years.
| Road Exposures | Total (n = 858) | without Asthma by Age 5 Years (n = 623) | with Asthma by Age 5 Years (n = 235) | p-Value * | |
|---|---|---|---|---|---|
| Number of participants who moved, n (%) | 413 (48) | 288 (46) | 125 (53) | 0.07 | |
| Number of moves per participant, median (IQR) | 1 (1–2) | 1 (1–2) | 2 (1–2) | 0.04 | |
| Average length of stay in each address in days, median (IQR) | 1095 (548–1095) | 1095 (548–1095) | 548 (548–1095) | 0.05 | |
| Birth distance to major roads in meter, median (IQR) | 540 (236–1121) | 601 (253–1177) | 425 (211–960) | 0.006 | |
| Pooled distance to major roads in meter, median (IQR) | 601 (285–1199) | 651 (305–1218) | 507 (233–1082) | 0.005 | |
| Birth distance to primary roads in meter, median (IQR) | 3004 (1283–6275) | 3167 (1301–6398) | 2500 (1197–5885) | 0.15 | |
| Pooled distance to primary roads in meter, median (IQR) | 3430 (1491–7765) | 3558 (1516–8429) | 2908 (1483–6574) | 0.14 | |
| Birth major road density in km roadways/km2 land area, median (IQR) † | 5 (4–9) | 5 (4–9) | 6 (4–10) | 0.61 | |
| Pooled major road density in km roadways/km2 land area, median (IQR) †,§ | 4 (2–7) | 4 (2–6) | 4 (2–8) | 0.58 | |
| Birth primary road density in km roadways/km2 land area, median (IQR) † | 6 (3–11) | 6 (3–8) | 9 (3–21) | 0.35 | |
| Pooled primary road density in km roadways/km2 land area, median (IQR) †,§ | 4 (2–6) | 4 (2–6) | 2 (1–8) | 0.64 | |
| Birth population density in population/m2 land area, median (IQR) ‡ | 4432 (1817–10,611) | 3954 (1698–9615) | 5713 (2075–13,244) | 0.01 | |
| Pooled population density in (population/mile2 land area, median (IQR) ‡,§ | 4590 (2008–9793) | 4210 (1961–9004) | 6256 (2203–12,776) | 0.005 | |
| Birth distance to major roads, meters | <100 | 82 (10) | 55 (9) | 27 (11) | 0.08 |
| 100–200 | 105 (12) | 75 (12) | 30 (13) | ||
| 201–300 | 81 (9) | 51 (8) | 30 (13) | ||
| >300 | 589 (69) | 442 (71) | 147 (63) | ||
| Birth distance to primary roads, meters | <400 | 55 (6) | 37 (6) | 18 (8) | 0.59 |
| 400–1000 | 108 (13) | 77 (12) | 31 (13) | ||
| >1000 | 694 (81) | 509 (82) | 185 (79) | ||
| Pooled distance to major roads, meters § | <100 | 55 (6) | 35 (6) | 20 (9) | 0.08 |
| 100–200 | 74 (9) | 53 (8) | 21 (8) | ||
| 201–300 | 96 (11) | 62 (10) | 34 (14) | ||
| >300 | 633 (74) | 473 (76) | 160 (69) | ||
| Pooled distance to primary roads, meters § | <400 | 31 (4) | 22 (3) | 9 (4) | 0.83 |
| 400–1000 | 87 (10) | 61 (10) | 26 (11) | ||
| >1000 | 740 (86) | 540 (87) | 200 (5) | ||
Abbreviations: IQR = interquartile range. * All of the p-values obtained by excluding participants with any missing data. † Geographic information systems (GIS) based road measurements were done in a circular buffer area with a 250-radius surrounding the participants’ residential area. ‡ Population density of residential census block was assigned to each participant by weighted block centroid geographic retrieval. § Pooled estimates derived by weighting exposures according to duration spent each address up to age three or time outcome occurred, whichever happened first.