Table 1. Household and individual factors associated with blood-lead levels (BLL).
| Characteristics | No. of children | Mean blood level μg/dl | Multiple regression model |
|||
|---|---|---|---|---|---|---|
| Coefficienta (95% CI) | P-value | |||||
| Roof construction material | ||||||
| Strong | 760 | 6.3 | 0.13 | 0.323 | 0.323 | |
| Light | 800 | 8.1 | 0.36 | 0.009 | 0.009b | |
| Mixed but predominantly strong | 633 | 6.6 | 0.17 | 0.206 | 0.206 | |
| Mixed but predominantly light | 563 | 6.6 | 0.16 | 0.219 | 0.219 | |
| Mixed but predominantly salvaged | 32 | 6.6 | 0.54 | 0.010 | 0.010c | |
| Salvaged/makeshift | 60 | 4.7 | (referent category) | |||
| Water source | ||||||
| Own use, tubed/piped well | 178 | 5.9 | –0.16 | 0.052 | 0.052 | |
| Shared, tubed/piped well | 649 | 6.8 | –0.10 | 0.048 | 0.048c | |
| Dug well | 577 | 6.5 | –0.03 | 0.510 | 0.510 | |
| Spring, river, stream etc. | 134 | 6.9 | 0.05 | 0.554 | 0.554 | |
| Rain | 20 | 10.1 | 0.54 | 0.039 | 0.039c | |
| Peddler | 9 | 3.1 | –0.17 | 0.529 | 0.529 | |
| Others | 45 | 9.2 | 0.17 | 0.296 | 0.296 | |
| Communal water system | 1238 | 6.9 | (referent category) | |||
| Blood haemoglobin concentration | –0.04 | (–0.07, –0.02) | 0.001b | |||
| <11 g/dl | 672 | 7.8 | ||||
| 11–13 g/dl | 1622 | 6.8 | ||||
| >13 g/dl | 523 | 6.3 | ||||
| Blood folate concentration | –0.0001 | (–0.0003, 0.0002) | 0.583 | |||
| <1.20 ng/ml | 548 | 6.6 | ||||
| 1.20–1.40 ng/ml | 1294 | 7.2 | ||||
| >2.40 ng/ml | 1018 | 6.3 | ||||
| HOME percentage score | –0.01 | (–0,02, –0.01) | <0.00b | |||
| Low (<50%) | 2503 | 6.7 | ||||
| Middle (50-75%) | 12 | 7.0 | ||||
| High (>75%) | 2 | 2.2 | ||||
| Age | 0.03 | 0.000 | <0.001b | |||
| 6 months to 1 year | 443 | 5.9 | ||||
| 1 year | 1061 | 6.7 | ||||
| 2 years | 644 | 7.5 | ||||
| 3 years | 455 | 7.4 | ||||
| 4 years | 250 | 7.6 | ||||
| Age² | –0.0004 | 0.001 | <0.001b | |||
| Sex | –0.09 | 0.015 | 0.015c | |||
| Female | 1330 | 6.5 | ||||
| Male | 1530 | 7.3 | (referent category) | |||
| Birth weight | 0.00003 | (–0.00001, 0.00007) | 0.144 | |||
| <2500 g | 419 | 6.7 | ||||
| 2500–3500 g | 1293 | 6.6 | ||||
| >3500 g | 475 | 7.2 | ||||
| Breastfeeding | 0.22 | (0.09, 0.34) | 0.001c | |||
| History of breastfeeding | 2576 | 7.1 | ||||
| No breastfeeding | 274 | 5.7 | (referent category) | |||
| Urbanity | –0.10 | (–0.18, –0.02) | 0.019c | |||
| Rural | 1953 | 7.0 | ||||
| Urban | 907 | 6.8 | (referent category) | |||
| Income proxy | 0.15 | (0.03, 0.27) | 0.013c | |||
| Owns mobile phone | 535 | 7.1 | ||||
| Does not own mobile phone | 2303 | 6.9 | (referent category) | |||
| Household type | –0.08 | (–0.16, –0.002) | 0.044c | |||
| Follow-home | 1425 | 6.9 | ||||
| Random | 1435 | 6.9 | (referent category) | |||
CI, confidence interval. a These coefficients indicate percentage changes of the blood-lead level for every unit change of the regressors. A coefficient of 0.10 indicates that 1 unit increase in a continuous explanatory variable results in an estimated 10% increase in BLL. Similarly, a coefficient of 0.10 for a categorical variable indicates that BLL for the associated category is estimated to be 10% higher than that for the reference category. Individual p-values for categorical variables are derived from the t-statistics of individual regression terms. b Statistical significance at P = <0.001 level. c Statistical significance at P = <0.05 level.