Table 1.
Characteristics of Baltimore Memory Study Participants at Baseline, 2001–2003
| Variable | Total Sample (N = 1,001) | Neighborhood Psychosocial Hazards Scale |
P Valuea | ||
| Lowest Tertile (n = 280) | Middle Tertile (n = 387) | Highest Tertile (n = 334) | |||
| Individual-level variables | |||||
| Mean age, years (SD) | 59.4 (6.0) | 59.3 (5.7) | 59.4 (6.0) | 59.7 (6.1) | <0.001 |
| Women, no. (%) | 662 (65.9) | 191 (68.2) | 244 (63.1) | 226 (67.6) | 0.283 |
| Non-white race/ethnicity, no. (%) | 451 (44.9) | 57 (20.3) | 177 (45.7) | 216 (64.7) | <0.001 |
| Mean educational attainment, 9-level index (SD) | 4.9 (2.2) | 6.2 (1.9) | 4.8 (2.1) | 4.1 (2.0) | <0.001 |
| Mean tibia lead level, μg/g (SD) | 18.8 (11.1) | 16.3 (11.0) | 19.3 (10.7) | 20.3 (11.4) | <0.001 |
| Mean cognitive domain scores (SD)b | |||||
| Language | 0.01 (0.82) | 0.36 (0.70) | 0.02 (0.79) | −0.29 (0.85) | <0.001 |
| Processing speed | 0.06 (0.84) | 0.25 (0.66) | 0.07 (0.84) | −0.11 (0.95) | <0.001 |
| Eye-hand coordination | 0.02 (0.76) | 0.27 (0.61) | 0.03 (0.74) | −0.21 (0.83) | <0.001 |
| Executive functioning | 0.03 (0.71) | 0.30 (0.63) | 0.03 (0.74) | −0.18 (0.70) | <0.001 |
| Verbal learning and memory | 0.02 (0.89) | 0.24 (0.73) | 0.02 (0.87) | −0.15 (0.99) | <0.001 |
| Visual memory | 0.03 (0.85) | 0.23 (0.78) | 0.07 (0.86) | −0.19 (0.84) | <0.001 |
| Visuoconstruction | 0.04 (0.98) | 0.32 (0.85) | 0.10 (0.94) | −0.28 (1.05) | <0.001 |
Abbreviation: SD, standard deviation.
a
P values indicate whether the variable means or distributions differ across tertiles of the neighborhood psychosocial hazards scale; t tests were used for continuous variables and χ2 tests for categorical variables.
b
Cognitive domain scores depart from expected values (mean = 0, SD, 1) because z-transformation was performed by using data from all 1,140 study subjects at visit 1.