Table 4.
Relationship between blood lead level (BLL) and chronic pain in subgroups of potential effect modifiers
| Subgroups | BLL quartiles | P for interaction a | |||
|---|---|---|---|---|---|
| Q1 | Q2 OR (95% CI) P |
Q3 OR (95% CI) P |
Q4 OR (95% CI) P |
||
| Age, years | 0.679 | ||||
| < 55 | Reference | 1.11 (0.85, 1.45) 0.435 | 0.97 (0.73, 1.27) 0.799 | 1.10 (0.81, 1.48) 0.546 | |
| ≥ 55 | Reference | 1.09 (0.58, 2.04) 0.792 | 1.26 (0.71, 2.25) 0.426 | 1.30 (0.72, 2.33) 0.380 | |
| Gender | 0.668 | ||||
| Male | Reference | 1.33 (0.79, 2.24) 0.284 | 1.44 (0.88, 2.35) 0.152 | 1.68 (1.01, 2.77) 0.044 | |
| Female | Reference | 1.21 (0.91, 1.60) 0.186 | 1.12 (0.83, 1.52) 0.444 | 1.12 (0.78, 1.61) 0.535 | |
| Race | 0.121 | ||||
| Non-Hispanic white | Reference | 1.42 (1.05, 1.93) 0.023 | 1.31 (0.96, 1.80) 0.093 | 1.64 (1.16, 2.33) 0.005 | |
| Non-Hispanic Black | Reference | 1.76 (0.91, 3.40) 0.095 | 1.84 (0.95, 3.55) 0.069 | 2.25 (1.10, 4.62) 0.027 | |
| Mexican American | Reference | 0.54 (0.29, 0.98) 0.043 | 0.74 (0.43, 1.29) 0.291 | 0.61 (0.33, 1.12) 0.111 | |
| Others | Reference | 1.27 (0.32, 4.96) 0.732 | 1.69 (0.46, 6.20) 0.426 | 1.22 (0.29, 5.19) 0.784 | |
| Marital status | 0.739 | ||||
| Married or living with others | Reference | 1.11 (0.82, 1.50) 0.495 | 1.10 (0.81, 1.49) 0.530 | 1.31 (0.94, 1.82) 0.117 | |
| Others | Reference | 1.36 (0.90, 2.06) 0.147 | 1.31 (0.86, 1.97) 0.206 | 1.33 (0.84, 2.09) 0.223 | |
| Education level | 0.654 | ||||
| Less than high school | Reference | 1.28 (0.68, 2.38) 0.442 | 1.48 (0.81, 2.72) 0.203 | 1.79 (0.96, 3.33) 0.066 | |
| High school or equivalent | Reference | 1.18 (0.74, 1.89) 0.492 | 0.95 (0.59, 1.52) 0.826 | 0.95 (0.56, 1.60) 0.834 | |
| College or above | Reference | 1.12 (0.81, 1.55) 0.478 | 1.18 (0.85, 1.64) 0.332 | 1.32 (0.91, 1.92) 0.147 | |
| PIR | 0.324 | ||||
| < 1 | Reference | 2.16 (1.15, 4.06) 0.017 | 1.27 (0.66, 2.47) 0.472 | 1.83 (0.92, 3.63) 0.085 | |
| 1–3 | Reference | 1.02 (0.68, 1.51) 0.940 | 1.01 (0.68, 1.50) 0.965 | 1.10 (0.71, 1.70) 0.669 | |
| > 3 | Reference | 1.12 (0.78, 1.60) 0.538 | 1.31 (0.92, 1.87) 0.140 | 1.38 (0.92, 2.07) 0.114 | |
| BMI | 0.954 | ||||
| < 25 | Reference | 1.09 (0.70, 1.71) 0.698 | 1.06 (0.67, 1.68) 0.799 | 1.20 (0.72, 1.98) 0.484 | |
| ≥ 25 | Reference | 1.22 (0.92, 1.63) 0.173 | 1.22 (0.92, 1.63) 0.174 | 1.35 (0.98, 1.85) 0.063 | |
| Daily physical activity | 0.751 | ||||
| Mainly sit | Reference | 1.05 (0.66, 1.68) 0.837 | 1.08 (0.68, 1.72) 0.747 | 0.99 (0.58, 1.69) 0.963 | |
| Walk around | Reference | 1.35 (0.96, 1.90) 0.089 | 1.23 (0.87, 1.74) 0.236 | 1.55 (1.06, 2.26) 0.023 | |
| Light load | Reference | 0.92 (0.51, 1.65) 0.775 | 1.41 (0.78, 2.54) 0.260 | 1.25 (0.65, 2.39) 0.503 | |
| Subgroups | BLL quartiles | P for interactiona | |||
|---|---|---|---|---|---|
| Q1 | Q2 OR (95% CI) P |
Q3 OR (95% CI) P |
Q4 OR (95% CI) P |
||
| Daily physical activity | |||||
| Heavy load | Reference | 1.32 (0.44, 3.95) 0.622 | 0.98 (0.33, 2.90) 0.971 | 1.31 (0.43, 4.01) 0.635 | |
| Smoking | 0.189 | ||||
| Less than 100 cigarettes in a lifetime | Reference | 0.94 (0.67, 1.33) 0.740 | 1.15 (0.82, 1.63) 0.423 | 1.23 (0.82, 1.84) 0.323 | |
| At least 100 cigarettes in a lifetime | Reference | 1.49 (1.05, 2.12) 0.026 | 1.24 (0.87, 1.76) 0.234 | 1.46 (1.00, 2.11) 0.047 | |
| Alcoholic drinks per day in past 12 months | 0.510 | ||||
| < 9 | Reference | 1.19 (0.93, 1.52) 0.163 | 1.20 (0.94, 1.54) 0.143 | 1.34 (1.02, 1.75) 0.034 | |
| ≥ 9 | Reference | 1.35 (0.20, 9.07) 0.759 | 0.55 (0.09, 3.42) 0.519 | 0.86 (0.12, 6.24) 0.882 | |
| Hypertension | 0.018 | ||||
| No | Reference | 0.98 (0.74, 1.30) 0.888 | 1.00 (0.75, 1.33) 0.999 | 1.16 (0.85, 1.59) 0.352 | |
| Yes | Reference | 2.33 (1.41, 3.85) 0.001 | 1.99 (1.21, 3.26) 0.007 | 1.94 (1.14, 3.30) 0.014 | |
| Diabetes | 0.313 | ||||
| No | Reference | 1.17 (0.91, 1.50) 0.221 | 1.14 (0.88, 1.47) 0.328 | 1.33 (1.01, 1.76) 0.043 | |
| Yes | Reference | 1.74 (0.71, 4.29) 0.229 | 1.95 (0.81, 4.67) 0.137 | 1.32 (0.49, 3.51) 0.581 | |
| Coronary heart disease | 0.332 | ||||
| No | Reference | 1.19 (0.93, 1.52) 0.162 | 1.19 (0.93, 1.52) 0.171 | 1.35 (1.03, 1.78) 0.030 | |
| Yes | Reference | 1.09 (0.20, 5.95) 0.925 | 0.83 (0.17, 4.00) 0.812 | 0.51 (0.10, 2.46) 0.400 | |
| Arthritis | 0.004 | ||||
| No | Reference | 1.13 (0.86, 1.49) 0.388 | 0.86 (0.64, 1.16) 0.323 | 1.03 (0.74, 1.44) 0.840 | |
| Yes | Reference | 1.56 (0.95, 2.56) 0.081 | 2.25 (1.39, 3.62) 0.001 | 2.35 (1.41, 3.92) 0.001 | |
| Osteoporosis | 0.649 | ||||
| No | Reference | 1.22 (0.95, 1.56) 0.118 | 1.19 (0.92, 1.53) 0.185 | 1.29 (0.98, 1.70) 0.071 | |
| Yes | Reference | 0.95 (0.32, 2.82) 0.929 | 1.17 (0.41, 3.31) 0.771 | 1.86 (0.59, 5.85) 0.289 | |
| Cancer or malignancy | 0.708 | ||||
| No | Reference | 1.16 (0.90, 1.48) 0.250 | 1.14 (0.88, 1.46) 0.319 | 1.26 (0.95, 1.67) 0.103 | |
| Yes | Reference | 2.11 (0.71, 6.25) 0.177 | 1.90 (0.68, 5.32) 0.223 | 2.36 (0.81, 6.86) 0.116 | |
BLL blood lead level. Bold text indicates a statistically significant difference with a P-value < 0.05
aP for interaction was calculated using the likelihood ratio test comparing models with and without the interaction term