Table 2.
Summary of cohort characteristics, and amoxicillin prescribing ratesa
| Baseline characteristic | Cohort, n/N (%), (N= 2493) | Amoxicillin prescribing rate/1000 child–years, rate (95% CI) | |
|---|---|---|---|
|
| |||
| Year 1 | Year 2 | ||
| Total | 710 (677 to 744) | 780 (745 to 816) | |
|
| |||
| Sex of infant | |||
| Male | 1264/2481 (50.9) | 776 (728 to 827) | 823 (774 to 875) |
| Female | 1217/2481 (49.1) | 642 (597 to 689) | 735 (688 to 786) |
| Missing | 12/2493 (0.5) | — | — |
|
| |||
| Mother’s ethnic background | |||
| White British | 920/2491 (36.9) | 529 (483 to 579) | 638 (587 to 692) |
| Pakistani, UK born | 438/2491 (17.6) | 845 (760 to 936) | 900 (813 to 994) |
| Pakistani, not UK born | 782/2491 (31.4) | 969 (901 to 1042) | 935 (868 to 1006) |
| Other | 351/2491 (14.1) | 436 (369 to 512) | 659 (576 to 751) |
| Missing | 2/2493 (0.1) | — | — |
|
| |||
| Socioeconomic status | |||
| Least deprived and most educated | 507/2483 (20.4) | 608 (541 to 680) | 704 (632 to 782) |
| Employed not materially deprived | 443/2491 (17.8) | 505 (440 to 576) | 711 (632 to 795) |
| Employed with no access to money | 446/2485 (17.9) | 641 (568 to 720) | 786 (705 to 874) |
| On benefits but coping | 717/2485 (28.9) | 872 (805 to 944) | 881 (813 to 953) |
| Most deprived | 372/2485 (15.0) | 856 (763 to 956) | 776 (688 to 872) |
| Missing | 8/2493 (0.3) | — | — |
|
| |||
| Mother smoking during pregnancy | |||
| No | 2147/2491 (86.2) | 724 (688 to 761) | 796 (758 to 835) |
| Yes | 344/2491 (13.8) | 617 (536 to 706) | 682 (596 to 777) |
| Missing | 2/2493 (0.1) | — | — |
|
| |||
| Congenital anomalies | |||
| No | 2409/2493 (96.6) | 702 (669 to 737) | 763 (728 to 799) |
| Yes | 84/2493 (3.4) | 940 (743 to 1173) | 1270 (1039 to 1537) |
| Missing | 0/2493 (0.5) | — | — |
|
| |||
| Gestational age | |||
| Term/late-term | 1796/2481 (72.4) | 703 (665 to 744) | 749 (710 to 791) |
| Early/preterm | 685/2481 (27.6) | 729 (666 to 796) | 862 (793 to 935) |
| Missing | 12/2493 (0.5) | — | — |
|
| |||
| Quarter of birth | |||
| January–March | 643/2493 (25.8) | 696 (632 to 764) | 731 (665 to 801) |
| April–June | 601/2493 (24.1) | 833 (761 to 910) | 775 (706 to 850) |
| July–September | 608/2493 (24.4) | 694 (629 to 765) | 805 (735 to 880) |
| October–December | 641/2493 (25.7) | 624 (565 to 690) | 810 (741 to 883) |
| Missing | 0/2493 (0.0) | — | — |
|
| |||
| Delivery mode | |||
| Vaginal | 1964/2481 (79.2) | 693 (656 to 731) | 768 (729 to 808) |
| Caesarean | 517/2481 (20.8) | 778 (703 to 859) | 829 (751 to 912) |
| Missing | 12/2493 (0.5) | — | — |
|
| |||
| Breastfeeding duration, months | |||
| <1 | 1096/2482 (44.2) | 774 (723 to 829) | 841 (787 to 898) |
| 1–<6 | 598/2482 (24.1) | 706 (639 to 777) | 765 (696 to 839) |
| ≥6 | 788/2482 (31.7) | 622 (567 to 680) | 714 (656 to 776) |
| Missing | 11/2493 (0.4) | — | — |
| Characteristics collected at 12 months and 24 months | Cohort, n/N % (N= 2493) | Amoxicillin prescribing rate/1000 child-years, rate (95% CI) | ||
|---|---|---|---|---|
|
|
|
|||
| Year 1 | Year 2 | Year 1 | Year 2 | |
| Quartile of PM2.5 in relation to Bradford levelb | ||||
| 1st/2nd quartile | 904/2493 (36.3) | 839/2476 (33.9) | 623 (573 to 678) | 802 (742 to 865) |
| 3rd quartile | 1116/2493 (44.8) | 1039/2476 (42.0) | 769 (718 to 822) | 784 (731 to 840) |
| 4th quartile | 473/2493 (19.0) | 598/2476 (24.2) | 738 (662 to 821) | 750 (681 to 824) |
| Missing | 0/2493 (0.0) | 17/2493 (0.7) | — | — |
|
| ||||
| Formal childcare attendance | ||||
| No | 2038/2482 (82.1) | 1511/1935 (78.1) | 746 (708 to 784) | 793 (748 to 839) |
| Yes | 444/2482 (17.9) | 424/1935 (21.9) | 553 (485 to 627) | 852 (766 to 945) |
| Missing | 11/2493 (0.4) | 558/2493 (22.4) | — | — |
|
| ||||
| Household mould/damp | ||||
| No mould or damp | 1912/2475 (77.3) | 1571/2001 (78.5) | 702 (665 to 741) | 808 (764 to 854) |
| Mould or damp | 563/2475 (22.7) | 430/2001 (21.5) | 746 (676 to 822) | 803 (720 to 893) |
| Missing | 18/2493 (0.7) | 492/2493 (19.7) | — | — |
|
| ||||
| Number of people in household | ||||
| 2–5 | 1719/2482 (69.3) | 1343/1994 (67.4) | 593 (557 to 631) | 705 (666 to 747) |
| ≥6 | 763/2482 (30.7) | 651/1994 (32.6) | 977 (908 to 1050) | 948 (880 to 1020) |
| Missing | 11/2493 (0.4) | 499/2493 (20.0) | — | — |
|
| ||||
| Cooking type | ||||
| Electric cooking only | 312/2481 (12.6) | 226/2002 (11.3) | 560 (480 to 651) | 635 (534 to 750) |
| Electric and gas cooking | 467/2481 (18.8) | 361/2002 (18.0) | 569 (502 to 643) | 699 (614 to 791) |
| Gas cooking only | 1702/2481 (68.6) | 1415/2002 (70.7) | 777 (735 to 821) | 862 (814 to 912) |
| Missing | 12/2493 (0.5) | 491/2493 (19.7) | — | — |
a
Amoxicillin prescribing rates per 1000 child–years during the first 2 years of life for the total cohort, and summarised according to exposure categories.
b
PM2.5 exposure for year 1 represents exposure in utero and year 2 represents exposure during the first year. The median and IQR for the absolute PM2.5 levels corresponding to each quartile are displayed in Supplementary Table S3. IQR = interquartile range. PM2.5 = particulate matter ≤2.5 µm.