Table 5.
Repeated-measures mixed model for log-transformed creatinine-adjusted urinary mercury concentration (U-Hg) at baseline and at first and second follow-up surveys
| Characteristic | Current U-Hg concentration* |
Cumulative U-Hg concentration† |
||
|---|---|---|---|---|
| β (SE) | P-value | β (SE) | P-value | |
| Amalgam-filled tooth surface | 0.028 (0.004) | <0.001 | 0.022 (0.002) | <0.001 |
| Gender | ||||
| Male | ref. | ref. | ||
| Female | −0.033 (0.037) | 0.371 | −0.058 (0.041) | 0.164 |
| Monthly income (million won per month) | ||||
| <2 | ref. | ref. | ||
| 2–3 | 0.042 (0.048) | 0.391 | 0.014 (0.054) | 0.799 |
| >3 | −0.014 (0.050) | 0.775 | −0.010 (0.057) | 0.854 |
| Education | ||||
| Father | ||||
| ≤High school | ref. | ref. | ||
| >High school | −0.020 (0.044) | 0.645 | −0.029 (0.049) | 0.559 |
| Mother | ||||
| ≤High school | ref. | ref. | ||
| >High school | 0.001 (0.044) | 0.980 | 0.003 (0.050) | 0.959 |
| Job | ||||
| Father | ||||
| Unemployed | ref. | ref. | ||
| Manual worker | −0.182 (0.108) | 0.093 | −0.184 (0.121) | 0.130 |
| Non-manual worker | −0.198 (0.108) | 0.069 | −0.193 (0.121) | 0.112 |
| Mother | ||||
| Unemployed | ref. | ref. | ||
| Manual worker | 0.088 (0.077) | 0.250 | 0.099 (0.083) | 0.234 |
| Non-manual worker | 0.061 (0.038) | 0.104 | 0.063 (0.042) | 0.135 |
| Frequency of brushing per day | ||||
| ≤1 | ref. | ref. | ||
| 2 | 0.139 (0.074) | 0.059 | 0.093 (0.081) | 0.255 |
| ≥3 | 0.100 (0.075) | 0.181 | 0.057 (0.083) | 0.494 |
| Visited a dentist within the previous 6 months | ||||
| No | ref. | ref. | ||
| Yes | 0.046 (0.038) | 0.218 | 0.013 (0.042) | 0.752 |
| Frequency of chewing gum per week | ||||
| Hardly ever | ref. | ref. | ||
| More than once | 0.062 (0.037) | 0.094 | 0.071 (0.041) | 0.086 |
| Frequency of fish intake per week | ||||
| Hardly ever | ref. | ref. | ||
| 1–2 | −0.087 (0.047) | 0.068 | −0.114 (0.053) | 0.033 |
| ≥3 | −0.069 (0.064) | 0.277 | −0.126 (0.071) | 0.078 |
*
U-Hg concentration and amalgam-filled tooth surface were examined at each survey.
†
Sum of the current U-Hg concentration measured at each survey and the U-Hg concentrations of previous surveys. Cumulative U-Hg was calculated for first and second follow-up surveys only.
SE, standard error.