Table 1.
Comparison of the Exposure, Cognitive, and Health Outcome Scores and the Sociodemographic Background Variables, United Kingdom RANCH Project, 2001–2003
| Characteristic | Subsample With Air Pollution Data (n = 719) |
Sample Without Air Pollution Data (n = 241) |
Difference Between the Samples With and Without Air Pollution Dataa |
||||||
|---|---|---|---|---|---|---|---|---|---|
| Range | Mean (SD) | % | Range | Mean (SD) | % | t | χ2 | P Value | |
| Exposure data | |||||||||
| Aircraft noise exposure at school, dBA | 34–68 | 54 (10.6) | 46–59 | 52 (3.83) | 3.60 | <0.01 | |||
| Road traffic noise exposure at school, dBA | 37–67 | 50 (7.7) | 47–63 | 52 (5.04) | −4.78 | <0.01 | |||
| Nitrogen dioxide at school, μg/m3 | 29.41–79.88 | 42.73 (10.60) | N/A | N/A | |||||
| Cognitive outcomes | |||||||||
| Reading comprehension | −1.49–2.51 | 0.20 (1.13) | −1.49–2.51 | 0.23 (1.11) | −0.36 | 0.72 | |||
| Recognition memory | 15–30 | 25.10 (2.63) | 14–30 | 24.78 (2.75) | 1.54 | 0.12 | |||
| Information recall | 0–30.5 | 19.02 (5.31) | 0–29 | 18.06 (5.86) | 2.30 | 0.02 | |||
| Conceptual recall | 0–7.5 | 5.25 (1.37) | 0–7.5 | 5.04 (1.53) | 1.93 | 0.06 | |||
| Working memory | −11–32 | 15.02 (7.37) | −13–32 | 14.50 (7.85) | 0.84 | 0.40 | |||
| Health outcomes | |||||||||
| Overall Strengths and Difficulties Questionnaire score | 0–34 | 10.16 (6.02) | 0–29 | 9.79 (5.63) | 0.81 | 0.42 | |||
| Very good/good self- rated health | 82.7 | 80.8 | 4.43 | 0.51 | |||||
| Fair/poor/very poor self-rated health | 17.3 | 19.2 | |||||||
| Systolic blood pressureb | 85–141 | 108.4 (10.1) | 91–135 | 110.5 (8.0) | −1.89 | 0.06 | |||
| Diastolic blood pressureb | 49–106 | 67.1 (8.1) | 46–82 | 66.9 (7.5) | 0.16 | 0.87 | |||
| Sociodemographic factors | |||||||||
| Age | 8 years, 10 months–11 years, 11 months | 10 years, 3 months | 8 years, 10 months–11 years, 11 months | 10 years, 3 months | −0.78 | 0.43 | |||
| Male | 45.6 | 43.6 | 0.30 | 0.58 | |||||
| Female | 54.4 | 56.4 | |||||||
| Parent(s) not employed | 22.7 | 22.9 | 0.004 | 0.95 | |||||
| Parent(s) employed | 77.3 | 77.1 | |||||||
| Home overcrowded | 21.7 | 25.7 | 1.53 | 0.22 | |||||
| Home not owned/ mortgaged | 42.5 | 41.0 | 0.16 | 0.67 | |||||
| Child has long- standing illness | 26.6 | 25.7 | 0.07 | 0.79 | |||||
| Child speaks other language at home | 20.3 | 27.0 | 4.67 | 0.03 | |||||
| Classroom has single window glazing | 57.3 | 74.7 | 73.23 | <0.01 | |||||
| Mother's educational levelb | 0.004–0.853 | 0.48 (0.28) | 0.004–0.853 | 0.56 (0.28) | −4.28 | <0.01 | |||
| Parental support scale | 4–12 | 10.2 (2.0) | 5–12 | 10.2 (1.9) | −0.40 | 0.69 | |||
| Small blood pressure cuff sizec | 5.8 | 1.3 | 2.55 | 0.11 | |||||
| Low birth weight (<2,500 g)c | 9.4 | 8.0 | 0.14 | 0.71 | |||||
| Premature birth (before gestational week 36)c | 12.0 | 14.7 | 0.40 | 0.53 | |||||
| Parent(s) with high blood pressureb | 20.3 | 25.3 | 0.89 | 0.35 | |||||
| Body mass indexc,d | 9–23 | 13.3 (2.32) | 10–18 | 13.0 (1.71) | 1.31 | 0.19 | |||
| Temperature during blood pressure measurement, °Cc | 20–27 | 22.9 (1.63) | 21–26 | 23.8 (1.35) | −4.47 | <0.01 | |||
Abbreviations: dB(A), sound level in decibels A-weighted to approximate the typical sensitivity of the human ear; N/A, not applicable; RANCH, Road Traffic and Aircraft Noise Exposure and Children's Cognition and Health; SD, standard deviation.
a χ2 tests were used for categorical variables and t tests were used for continuous variables to detect differences between the samples with and without air pollution data.
b Measured using a relative inequality index based on a ranked index of standard qualifications in each country resulting in a standardized score ranging from 0.01 to 1.00.
c These factors were only included as confounders/covariates in the blood pressure regression models and the numbers were reduced. There were 276 for whom we had air pollution data and 75 for whom we did not.
d Weight (kg)/height (m)2.