Table 2

Comparison of the participants with and without dry eye symptoms in terms of general characteristics, socioeconomic status and blood mercury levels

VariableDry eye symptom
NoYes
Weighted NumberW %* (mean)SE†Weighted NumberW %* (mean)SEp Value
Age (years)(39.6)(0.2)(39.7)(0.6)0.861
 <303 311 99030.20.8532 74232.72.30.242
 30–392 408 52622.00.6308 55818.91.8
 40–492 535 77023.20.6363 24322.32.1
 50–591 799 28716.40.5261 05416.01.7
 60–69811 3137.40.3140 5838.61.0
 ≥7086 0770.80.124 6211.50.4
Gender
 Men6 853 98862.60.7658 57840.42.4<0.001
 Women4 098 97637.40.7972 22539.62.4
Education status (years)†
 <6949 9248.90.5206 87112.91.60.062
 6–9969 9009.20.5126 3977.91.3
 10–124 844 63845.61.0688 55343.02.6
 >123 853 29736.31.0579 42136.22.4
Household income‡
 1Q1 225 03611.40.6208 96213.01.80.516
 2Q3 068 39428.41.0415 44425.82.2
 3Q3 368 98031.21.0483 92830.12.3
 4Q3 136 60029.01.0500 17231.12.5
Smoking status
 Non-smoker5 249 12547.90.9983 94860.32.2<0.001
 Ex-smoker2 181 99119.90.7282 82117.31.8
 Current smoker3 521 84732.20.9364 03322.32.1
Heavy alcohol drinking§
 No8 344 96977.90.81 386 13386.01.7<0.001
 Yes2 366 81422.10.8226 25314.01.7
Sleep time (h)
 ≥69 587 63187.50.71 389 16485.21.70.179
 <61 365 33312.50.7241 63814.81.7
Perceived stress status¶
 No7 998 42975.20.91 078 31667.62.30.001
 Yes2 642 97824.80.9517 49632.42.3
Cholesterol** (mg/dL)(186.4)(0.7)(187.4)(1.9)0.607
 <2409 274 28589.70.61 392 65389.71.40.517
 ≥2401 060 49410.30.6175 88010.31.4
Anaemia0.823
 No10 322 54494.30.41 521 03593.31.1
 Yes628 6215.70.4109 7676.71.1
Atopy history
 No10 552 82096.30.41 570 41996.31.00.963
 Yes400 1443.70.460 3833.71.0
Blood mercury level
 <Median5 953 40754.41.1787 03748.32.50.021
 ≥Median4 999 55745.71.1843 76551.72.5
  • 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 discriminated between participants with ‘low’ and ‘high’ blood mercury levels were 4.26 and 2.89 µg/L for males and females, respectively.

  • The p values were obtained by comparing the participants with and without dry eye symptoms using Rao-Scott χ2 analysis.

  • *Weighted per cent.

  • †124 missing values.

  • ‡60 missing values.

  • §88 missing values.

  • ¶116 missing values.

  • **220 missing values.