Table 2.
Characteristics of Participants Included in Analyses in Each Follow-up Period
| Enrollment | 6 yr | 11 yr | 16 yr | 22 yr | 26 yr | 32 yr | |
|---|---|---|---|---|---|---|---|
| n | 1,137* | 479† | 550† | 432† | 416† | 358† | 234† |
| CC16, ng/ml, GM (GSD) |
7.9 (1.5) | 7.5 (1.5) | 8.4 (1.5) | 11.5 (1.5) | 9.5 (1.6) | 10.5 (1.5) | |
| NO2 at enrollment, ppb, median (IQR) | 11.0 (6.0) | 10.8 (6.3) | 10.9 (6.2) | 10.7 (6.2) | 10.8 (6.2) | 10.7 (6.0) | 10.8 (6.2) |
| NO2 at age 6, ppb, median (IQR) | 10.5 (6.5) | 10.8 (6.5) | 10.7 (6.4) | 10.5 (6.4) | 10.3 (6.4) | 10.4 (6.9) | |
| Child sex, % (n) | |||||||
| M | 48.3 (550) | 49.9 (239) | 48.7 (268) | 48.8 (211) | 48.5 (204) | 47.2 (169) | 43.6 (102) |
| F | 51.6 (587) | 50.1 (240) | 51.3 (282) | 51.2 (221) | 51.5 (217) | 52.8 (189) | 56.4 (132) |
| Child ethnicity race, % (n) |
|||||||
| Non-Hispanic white | 59.4 (675) | 62.2 (298) | 58.6 (322) | 60.2 (260) | 61.3 (255) | 62.0 (222) | 60.3 (141) |
| Any Hispanic | 25.5 (290) | 27.8 (133) | 31.5 (173) | 29.6 (128) | 29.6 (123) | 28.5 (102) | 30.3 (71) |
| Any black | 4.1 (47) | 3.6 (17) | 3.3 (18) | 3.2 (14) | 2.2 (9) | 2.5 (9) | 2.6 (6) |
| Other | 11.0 (125) | 6.4 (31) | 6.7 (37) | 6.9 (30) | 7.0 (29) | 7.0 (25) | 6.8 (16) |
| Maternal age at enrollment, % (n) |
|||||||
| <20 | 5.1 (58) | 4.4 (21) | 4.5 (25) | 3.2 (14) | 3.1 (13) | 3.3 (12) | 2.1 (5) |
| 20–25 | 32.1 (365) | 29.4 (141) | 29.6 (163) | 29.9 (129) | 29.3 (122) | 33.5 (120) | 33.8 (79) |
| 26–30 | 38.2 (434) | 40.1 (192) | 40.2 (221) | 43.1 (186) | 42.3 (176) | 38.5 (138) | 40.2 (94) |
| >30 | 24.6 (280) | 26.1 (125) | 25.6 (141) | 23.8 (103) | 25.2 (105) | 24.6 (88) | 23.9 (56) |
| Maternal education at enrollment, % (n) |
|||||||
| ≤12 yr | 31.3 (355) | 28.2 (135) | 28.2 (155) | 24.6 (106) | 25.0 (104) | 25.1 (90) | 25.8 (60) |
| >12 yr | 68.7 (780) | 71.8 (344) | 71.8 (394) | 75.4 (325) | 75.0 (312) | 74.9 (268) | 74.3 (173) |
| Maternal smoking at enrollment, % (n) |
|||||||
| Yes | 17.2 (195) | 15.1 (72) | 14.2 (78) | 13.7 (59) | 13.9 (58) | 15.1 (54) | 13.7 (32) |
| No | 82.8 (941) | 84.9 (406) | 85.8 (471) | 86.3 (373) | 86.1 (358) | 84.9 (304) | 86.3 (202) |
| Current smoking, % (n) |
|||||||
| Yes | — | — | — | 10.6 (43) | 28.9 (120) | 26.0 (92) | 16.7 (39) |
| No | — | — | — | 89.4 (362) | 71.1 (296) | 74.0 (262) | 83.3 (195) |
Definition of abbreviations: CC16 = club cell secretory protein; GM = geometric mean; GSD = geometric standard deviation; IQR = interquartile range; NO2 = nitrogen dioxide.
Included participants had at least one CC16 measurement between age 6 and 32 years and their NO2 exposure at enrollment or age 6 could be determined from their address. Participants were asked about their own smoking status beginning at age 16.
Number of participants with ≥1 CC16 measurement between age 6 and 32 years and NO2 exposure was determined at enrollment address.
Number of participants with a CC16 measurement obtained during that follow-up period and their NO2 exposure at enrollment or age 6 could be determined from their address.