Table 1

General characteristics, socioeconomic status and blood mercury levels of the study cohort

VariablesNo.Weighted No.Weighted meanWeighted %SE
Age (years)39.60.2
 <3010153 844 73230.60.8
 30–399992 717 08521.60.6
 40–4910182 899 01323.00.5
 50–599382 060 34216.40.5
 60–69696951 8967.60.3
 ≥7096110 6980.90.1
Gender
 Men24987 512 56659.70.6
 Women22635 071 20040.30.6
Education status (years)*
 <66391 156 7959.50.5
 6–94531 096 2978.90.5
 10–1218495 533 19145.30.9
 >1216964 432 71836.30.9
Household income†
 1Q5691 433 99811.60.6
 2Q12823 483 83928.11.0
 3Q14193 852 90831.00.9
 4Q14313 636 77229.31.0
Smoking status
 Non-smoker25666 233 07349.50.8
 Ex-smoker9542 464 81219.60.7
 Current smoker12413 885 88130.90.8
Heavy alcohol drinking‡
 No38189 731 10279.00.7
 Yes8552 593 06721.00.7
Sleep time (h)
 ≥6413110 976 79587.20.6
 <66301 606 97112.80.6
Perceived stress status§
 No34919 076 74574.20.8
 Yes11543 160 47425.80.8
Cholesterol (mg/dL)¶186.50.7
 <240396310 666 93889.60.5
 ≥2405781 236 37410.40.5
Atopy history
 No462412 123 23996.30.4
 Yes137460 5273.70.4
Anaemia
 No444311 843 57994.10.4
 Yes317738 3885.90.4
Dry eye (symptoms)
 No410310 952 96487.00.7
 Yes6581 630 80213.00.7
Blood mercury levels3.70.0
 <Median23796 740 44453.61.0
 ≥Median23825 843 32246.41.0
  • Anaemia was defined as follows; for males with a haemoglobin level <13 g/dL, pregnant females with a haemoglobin level <11 g/dL, and non-pregnant females with a haemoglobin level <12 g/dL.

  • The median cut-off levels that discriminate between subjects with ‘low’ and ‘high’ blood mercury levels were 4.26 and 2.89 µg/L for males and females, respectively.

  • *124 missing values.

  • †60 missing values.

  • ‡88 missing values.

  • §116 missing values.

  • ¶220 missing values.