Table 1.
Description of the selected sample population of Malaysian schoolchildren
| Characteristics | Number opted out of study (n = 721)I, a |
Number consented to salivary cotinine study (n=1064)II |
TotalIII (n = 1785) |
|---|---|---|---|
| Mean age (years ± SD) | 10.7 ± 0.6 | 10.7 ± 0.6 | 10.7 ± 0.6 |
| Gender | |||
| Boys | 316 (43.8) | 448 (42.1) | 764 (42.8) |
| Girls | 380 (52.7) | 605 (56.7) | 985 (55.2) |
| Missing | 25 (3.5) | 11 (1.0) | 36 (2.0) |
| Family structure | |||
| Both parents | 651 (90.3) | 997 (93.7) | 1648 (92.3) |
| Single parent | 21 (2.9) | 27 (2.6) | 48 (2.7) |
| Others | 30 (4.1) | 40 (3.8) | 70 (3.9) |
| Missing | 19 (2.6) | - | 19 (1.1) |
| Ethnicity | |||
| Malay | 635 (88.1) | 958 (90.0) | 1593 (89.2) |
| Others | 67 (9.3) | 106 (10.0) | 173 (9.7) |
| Missing | 19 (2.6) | - | 19 (1.1) |
| Location | |||
| Urban | 435 (60.3) | 688 (64.7) | 1123 (62.9) |
| Rural | 286 (39.7) | 376 (35.3) | 662 (37.1) |
| Home smoking characteristics++ | |||
| Non-smoking households | 377 (52.3) | 446 (41.9) | 823 (46.1) |
| Smoking households | 290 (40.2) | 501 (47.1) | 791 (44.3) |
| Missing | 54 (7.5) | 117 (11.0) | 171 (9.6) |
| Family income++ | |||
| Low | 319 (44.2) | 529 (49.7) | 847 (47.6) |
| Medium | 274 (38.0) | 326 (30.6) | 601 (33.7) |
| High | 88 (12.2) | 144 (13.5) | 232 (13.0) |
| Missing | 40 (5.5) | 65 (6.1) | 105 (5.9) |
Values are in numbers (percentages)
SD: Standard Deviation
Chi-square test performed between column I and II (excluding missing values)
++: Chi-square outcome for column I and II was p < 0.05 for home smoking characteristics and family income group
** The 3 categories in the variable Family income was derived using cut-off points obtained from the recent data of Economic Planning Unit, Prime Minister Department Malaysia. The average income is RM3686. Family income lower than RM3000 per month is categorised as low income, RM3000 to RM5000 is categorised as middle income and income of more than RM5000 is categorised as high income group
a Column I represents 721 children which includes 531 children who opted out of the study, 82 children whose saliva samples could not be collected and108 children who did not provide sufficient saliva sample for laboratory analysis