Table 1.
Participant characteristics
| Mean ± SD or number and (%) Median (IQR) |
p-value 1 | ||
|---|---|---|---|
| Included (N= 408) | Excluded (N=692) | ||
| Blood lead 3-5 years | 6.63 ± 2.64 | 6.33 ± 2.64 | 0.059 |
| 6.4 (4.9 - 8) | 6.1 (4.6 - 7.6) | ||
| Blood lead 12 years | 3.10 ± 1.17 | 3.12 ± 1.17 | 0.832 |
| 2.9 (2.3-3.6) | 29.9 (2.3-3.7) | ||
| Father’s Occupation | 0.369 | ||
| Unemployed | 19 (4.66%) | 33 (3.87%) | |
| Unskilled/skilled labor | 241 (59.07%) | 477 (55.92%) | |
| Professional | 148 (36.27%) | 343 (40.21%) | |
| Mother’s Occupation | 0.005 | ||
| Unemployed | 120 (29.41%) | 218 (25.29%) | |
| Unskilled/skilled labor | 191 (46.81%) | 363 (42.11%) | |
| Professional | 97 (23.77%) | 281 (32.60%) | |
| Age at HRV test | 11.52 ±0.36 | 11.54 ±0.40 | 0.305 |
| 11.48 (11.25-11.75) | 11.51 (11.27-11.80) | ||
| Sex | 0.439 | ||
| Male | 219 (53.68%) | 546 (55.94%) | |
| Female | 189 (46.32%) | 430 (46.32%) | |
| Serum Fe | 8.15 ± 0.82 | 8.12 ± 0.83 | 0.574 |
| 8.06 (7.59-8.62) | 8.06 (7.51-8.66) | ||
| Neighborhood Conditions | 0.425 | ||
| Crowded | 183 (44.85%) | 336 (47.32%) | |
| Not Crowded | 225 (55.15%) | 374 (52.68%) | |
| Planning Phase HRV LF/HF | 1.91 ± 1.54 | 1.94 ± 1.65 | 0.844 |
| 1.55 (0.79-2.51) | 1.42 (0.73-2.60) | ||
| Speaking Phase HRV LF/HF | 2.30 ± 1.43 | 2.27 ± 1.61 | 0.813 |
| 1.97 (1.26-2.91) | 1.80 (1.29-2.96) | ||
1
Comparison tests included t tests and chi-square tests for continuous and categorical variables, respectively.
Notes. Planning and Speaking phase LF/HF are measures of heart rate variability, a physiological stress response, assessed at the two time points during the Public Speaking Stress tasks. A high ratio represents lower heart rate variability, which is a dysregulated stress response indicative of dysfunction.
BLLs: Blood lead levels; HF: high frequency power band; IQR: Interquartile range; LF: low frequency power band; LF/HF: low frequency/high frequency ratio