Table 1.
Description of study population at baselinea
| Variable | No. (%) | FEV Mean (SD) |
FVC Mean (SD) |
FEV/FVC Mean (SD) |
|---|---|---|---|---|
| Sex | ||||
| Boys | 1634 (50) | 1812 (375) | 2107 (444) | 0.8625 (0.0593) |
| Girls | 1639 (50) | 1729 (415) | 1955 (459) | 0.8850 (0.0598) |
| Age | ||||
| <7 | 1440 (44) | 1572 (315) | 1812 (364) | 0.8696 (0.0632) |
| 7 to 9 | 1531 (47) | 1890 (368) | 2163 (430) | 0.8766 (0.0580) |
| >10 | 282 (9) | 2126 (419) | 2429 (488 | 0.8779 (0.0600) |
| Asthma | ||||
| No | 3174 (97) | 1567 (321) | 1789 (362) | 0.8776 (0.0581) |
| Yes | 99 (3) | 1540 (300) | 1836 (396) | 0.8457 (0.0785) |
| Home type | ||||
| Single-story house | 839 (26) | 1493 (326) | 1717 (362) | 0.8699 (0.0619) |
| Apartment building | 2191 (67) | 1590 (313) | 1815 (358) | 0.8779 (0.0589) |
| Other | 230 (7) | 1608 (337) | 1813 (377) | 0.8880 (0.0457) |
| No. of rooms | ||||
| <3 | 1530 (47) | 1540 (320) | 1760 (363) | 0.8768 (0.0584) |
| ≥3 | 1743 (53) | 1589 (320) | 1816 (361) | 0.8764 (0.0596) |
| Father’s education | ||||
| > Primary school | 3088 (94) | 1569 (320) | 1793 (362) | 0.8765 (0.0592) |
| ≤ Primary school | 185 (6) | 1521 (330) | 1735 (372) | 0.8776 (0.0565) |
| Mother’s education | ||||
| > Primary school | 3027 (92) | 1575 (318) | 1799 (361) | 0.8771 (0.0590) |
| ≤ Primary school | 246 (8) | 1461 (333) | 1682 (374) | 0.8698 (0.0592) |
| Father’s Occupation | ||||
| Manual laborer | 1706 (52) | 1543 (322) | 1769 (360) | 0.8730 (0.0613) |
| Non Manual laborer | 1567 (48) | 1592 (317) | 1813 (365) | 0.8805 (0.0563) |
| Mother’s Occupation | ||||
| Manual laborer | 1745 (53) | 1547 (331) | 1776 (368) | 0.8714 (0.0614) |
| Non Manual laborer | 1528 (47) | 1589 (307) | 1806 (357) | 0.8825 (0.0558) |
| Coal use | ||||
| No use | 2242 (69) | 1598 (303) | 1820 (349) | 0.8798 (0.0565) |
| Either heating or cooking | 509 (16) | 1572 (355) | 1794 (398) | 0.8775 (0.0592) |
| Both heating and cooking | 514 (15) | 1427 (325) | 1657 (359) | 0.8612 (0.0666) |
| Presence of ventilation | ||||
| No | 791 (24) | 1614 (310) | 1835 (360) | 0.8823 (0.0552) |
| Yes | 2474 (76) | 1552 (323) | 1776 (363) | 0.8747 (0.0601) |
| Stove type | ||||
| Gas | 2401 (74) | 1590 (311) | 1816 (356) | 0.8777 (0.0582) |
| Other | 844 (26) | 1501 (340) | 1720 (374) | 0.8730 (0.0615) |
| Heating | ||||
| No | 1826 (56) | 1618 (311) | 1837 (360) | 0.8831 (0.0560) |
| Yes | 1435 (44) | 1502 (321) | 1732 (359) | 0.8681 (0.0617) |
| Heating type | ||||
| None/central/gas | 2207 (67) | 1599 (310) | 1819 (357) | 0.8813 (0.0565) |
| Coal stove/fire pit | 1066 (33) | 1499 (332) | 1730 (369) | 0.8667 (0.0630) |
| Duration of heating (months) | ||||
| 0 | 1846 (56) | 1617 (311) | 1836 (359) | 0.8832 (0.0560) |
| 1 | 534 (16) | 1608 (293) | 1825 (338) | 0.8829 (0.0523) |
| 2 | 889 (27) | 1437 (321) | 1674 (361) | 0.8591 (0.0652) |
| Air conditioning | ||||
| No | 2592 (79) | 1571 (332) | 1797 (374) | 0.8752 (0.0604) |
| Yes | 673 (21) | 1551 (272) | 1764 (317) | 0.8815 (0.0529) |
| Father smoker | ||||
| No | 802 (25) | 1560 (324) | 1773 (361) | 0.8805 (0.0565) |
| Yes | 2471 (75) | 1569 (320) | 1795 (364) | 0.8753 (0.0598) |
| Mother smoker | ||||
| No | 3240 (99) | 1568 (321) | 1791 (363) | 0.8768 (0.0591) |
| Yes | 33 (1) | 1446 (266) | 1686 (318) | 0.8596 (0.0520) |
| Area | ||||
| Guangzhou | ||||
| Urban | 415 (13) | 1792 (399) | 2044 (455) | 0.8785 (0.0588) |
| Sub-urban | 411 (14) | 1839 (388) | 2079 (450) | 0.8881 (0.0634) |
| Wuhan | ||||
| Urban | 280 (8) | 1850 (396) | 2078 (454) | 0.8927 (0.0488) |
| Sub-urban | 136 (3) | 1711 (368) | 1923 (425) | 0.8922 (0.0494) |
| Lanzhou | ||||
| Urban | 428 (14) | 1706 (428) | 1997 (502) | 0.8565 (0.0597) |
| Sub-urban | 428 (15) | 1603 (379) | 1876 (434) | 0.8558 (0.0610) |
| Chongqing | ||||
| Urban | 760 (20) | 1801 (347) | 2060 (415) | 0.8776 (0.0566) |
| Sub-urban | 415 (12) | 1862 (406) | 2149 (466) | 0.8688 (0.0648) |
a
Baseline is defined as the first lung function measurement over the course of the study.