Table 2.
Baseline Characteristics According to Quintiles of Mercury Exposure Among 6,045 US Men and Women in Two Separate Prospective Cohorts.
| Characteristic | Quintiles of Toenail Mercury Concentration* | |||||
|---|---|---|---|---|---|---|
| Q1 | Q2 | Q3 | Q4 | Q5 | P for Trend | |
| Mercury, median, μg/g | 0.09 | 0.16 | 0.23 | 0.33 | 0.64 | |
| Mercury, geometric mean, μg/g | 0.08 | 0.16 | 0.23 | 0.34 | 0.72 | |
| Age, years | 55.4±7.9 | 54.7±8.0 | 55.0±8.1 | 55.0±7.9 | 54.9±7.5 | 0.62 |
| Smoking,% | ||||||
| Never | 43 | 40 | 38 | 36 | 34 | <0.001 |
| Past | 26 | 28 | 31 | 33 | 35 | <0.001 |
| Current | 31 | 32 | 31 | 31 | 31 | 0.95 |
| Family history of myocardial infarction, % | 23 | 24 | 26 | 25 | 26 | 0.25 |
| Family history of hypertension, % | 36 | 34 | 34 | 33 | 36 | 0.73 |
| Diabetes mellitus, % | 1 | 1 | 1 | 2 | 1 | 0.35 |
| Hypercholesterolemia, % | 4 | 4 | 5 | 6 | 8 | <0.001 |
| Lipid-lowering medication use, % | 1 | 2 | 3 | 3 | 2 | 0.03 |
| Aspirin use, % | 27 | 28 | 28 | 28 | 26 | 0.32 |
| Body mass index, kg/m2 | 24.7±4.2 | 24.6±4.2 | 24.2±4.0 | 24.4±4.1 | 24.2±3.8 | 0.001 |
| Physical activity, METS/week | 13.5±19.4 | 13.5±19.0 | 14.9±20.0 | 15.5±23.1 | 19.0±25.1 | <0.001 |
| Alcohol, drinks/day | 0.4±0.8 | 0.5±0.8 | 0.6±1.0 | 0.7±1.0 | 0.8±1.1 | <0.001 |
| Toenail selenium, μg/g | 0.83±0.43 | 0.81±0.24 | 0.82±0.38 | 0.83±0.44 | 0.82±0.33 | 0.82 |
| Fish consumption, servings/week | 1.1±1.0 | 1.5±1.2 | 1.8±1.5 | 2.1±1.7 | 2.6±2.2 | <0.001 |
| EPA & DHA, mg/day | 126±115 | 163±126 | 204±176 | 232±197 | 280±224 | <0.001 |
| Processed meat, servings/day | 0.4±0.6 | 0.4±0.4 | 0.4±0.5 | 0.3±0.3 | 0.3±0.3 | <0.001 |
| Unprocessed red meat, servings/day | 0.8±0.5 | 0.7±0.5 | 0.7±0.6 | 0.6±0.4 | 0.5±0.4 | <0.001 |
| Vegetable, servings/day | 3.0±1.7 | 3.1±2.0 | 3.1±1.8 | 3.3±2.5 | 3.5±2.1 | <0.001 |
| Fruit, servings/day | 1.9±1.4 | 1.9±1.4 | 2.0±1.4 | 2.0±1.4 | 2.1±1.5 | 0.001 |
| Whole grains, g/day | 17.7±15.6 | 17.5±16.8 | 17.0±17.1 | 17.6±15.4 | 16.9±16.9 | 0.30 |
| Diastolic BP in 1986, mm Hg† | 78.5±7 | 78.2±7 | 78.5±7 | 78.5±7 | 78.6±7 | 0.50 |
| Systolic BP in 1986, mm Hg† | 127.2±11 | 126.5±11 | 126.8±11 | 126.7±11 | 125.8±11 | 0.01 |
| Diastolic BP in 1990, mm Hg | 78.3±8 | 77.7±8 | 77.9±9 | 77.9±9 | 77.9±8 | 0.58 |
| Systolic BP in 1990, mm Hg | 128.1±14 | 126.7±13 | 126.7±14 | 126.6±13 | 126.4±13 | 0.05 |
Values are mean±SD (continuous characteristics) or percent (categorical characteristics), except for toenail mercury which is median and geometric mean.
*
Based on sex-specific quintile cutpoints.
†
The year of BP assessment closest to the baseline toenail sampling in both cohorts (1982–83 in women; 1987 in men). In crude (i.e., not using sex-specific quintiles), higher mercury exposures were not associated with systolic BP in 1986 and were associated with higher diastolic BP in 1986 (not shown).