TABLE 1.

Sample characteristics by quartiles of plasma selenium: The 2000–2001 UK NDNS¹

		Quartile of plasma selenium, interval in μmol/L
	Overall	1st (0.60 to <0.98)	2nd (0.98 to <1.08)	3rd (1.08 to <1.20)	4th (1.20 to 2.79)	P-trend
n		250	253	271	268
Age, y	40.8 ± 12.8	38.3 ± 12.8	38.1 ± 12.6	41.8 ± 13.0	45.0 ± 11.7	<0.001
Gender/menopausal status, %
Male	48.5	42.9	49.5	47.2	54.4	0.12
Postmenopause female	16.2	15.1	13.3	15.7	20.8	0.01
Premenopause female	35.3	42.1	37.1	37.2	24.8	0.001
BMI, kg/m2	26.7 ± 5.0	26.1 ± 5.1	26.8 ± 5.6	26.7 ± 4.6	27.0 ± 4.5	0.38
Smoking status, %
Current	33.1	52.5	34.3	29.2	17.5	<0.001
Former	39.6	27.0	41.3	39.8	49.7	0.001
Never	27.3	20.5	24.4	31.0	32.8	0.001
Physical activity score	44.5 ± 8.2	44.4 ± 9.1	45.6 ± 9.9	44.2 ± 6.9	43.7 ± 6.3	0.09
Income group, (>£600/mo), %	36.9	21.2	34.5	41.4	49.7	<0.001
Education, (Higher education or degree), %	31.8	21.5	30.1	32.7	42.5	0.001
Vitamin/mineral supplements, %	39.1	34.5	39.2	34.8	48.2	<0.001
Plasma selenium, μmol/L	1.10 ± 0.19	0.88 ± 0.08	1.03 ± 0.03	1.13 ± 0.04	1.34 ± 0.17	—
Red blood cell selenium, μmol/L	1.65 ± 0.40	1.44 ± 0.27	1.59 ± 0.32	1.69 ± 0.36	1.88 ± 0.49	<0.001
Whole-blood GPx activity,2nmol·mg Hb−1·min−1	124.6 ± 29.9	117.5 ± 27.2	122.6 ± 28.7	128.6 ± 32.0	129.1 ± 29.8	<0.001
Daily food energy, kJ	7768.0 ± 2355.2	7469.7 ± 2340.5	7947.1 ± 2587.8	7714.9 ± 2354.8	7928.7 ± 2085.7	0.08
Total cholesterol intake, mg/d	260.7 ± 119.3	238.3 ± 118.2	258.6 ± 113.5	264.9 ± 117.0	279.8 ± 125.3	0.004
Total fat intake, g/d	74.9 ± 27.6	72.7 ± 26.8	77.2 ± 29.1	73.3 ± 27.4	76.3 ± 26.7	0.34
Poly/saturated fatty acids ratio	0.45 ± 0.17	0.42 ± 0.16	0.43 ± 0.15	0.46 ± 0.16	0.49 ± 0.21	0.002

¹Values are survey-weighted means ± SD or percentages for continuous or categorical variables; n = 1,042.

²GPx, glutathione peroxidase.