Serum selenium concentrations and hypertension in the US Population

Abstract

Background: Selenium is an antioxidant micronutrient with potential interest for cardiovascular disease prevention. Few studies have evaluated the association between selenium and hypertension, with inconsistent findings. We explored the relationship of serum selenium concentrations with blood pressure and hypertension in a representative sample of the US population.

Methods and results: We undertook a cross-sectional analysis of 2638 adults > or =40 years old who participated in the 2003 to 2004 National Health and Nutrition Examination Survey. Serum selenium was measured by inductively coupled plasma-dynamic reaction cell-mass spectrometry. Hypertension was defined as blood pressure > or =140/90 mm Hg or current use of antihypertensive medication. Mean serum selenium was 137.1 microg/L. The multivariable adjusted differences (95% CIs) in blood pressure levels comparing the highest (> or =150 microg/L) to the lowest (<122 microg/L) quintile of serum selenium were 4.3 (1.3 to 7.4), 1.6 (-0.5 to 3.7), and 2.8 (0.8 to 4.7) mm Hg for systolic, diastolic, and pulse pressure, respectively. The corresponding odds ratio for hypertension was 1.73 (1.18 to 2.53). In spline regression models, blood pressure levels and the prevalence of hypertension increased with increasing selenium concentrations up to 160 microg/L.

Conclusions: High serum selenium concentrations were associated with higher prevalence of hypertension. These findings call for a thorough evaluation of the risks and benefits associated with high selenium status in the United States.

Figure 1. Adjusted differences (95% confidence intervals) for blood pressure levels by serum selenium concentrations

Serum selenium was modeled as restricted quadratic splines with nodes at the 5^th, 50^th, and 95^th percentiles. Multivariable linear regression models were adjusted for sex, age (continuous), race / ethnicity (non-Hispanic White, non-Hispanic Black, Mexican American or other), education (high school or higher vs. less than high school), body mass index (continuous), smoking (never, former, current), cotinine (continuous), menopausal status (yes, no), use of vitamin / mineral supplements (yes, no), and use of antihypertensive medications (yes, no). Blood pressure levels at the 10^th percentile (115 µg/L) of the serum selenium distribution were used as reference. The histogram shows the distribution of selenium concentrations in the study population.

Figure 2. Adjusted odds ratios (95% confidence intervals) for hypertension by serum selenium concentrations

Serum selenium was modeled as restricted quadratic splines with nodes at the 5^th, 50^th, and 95^th percentiles. The multivariable logistic regression model was adjusted for sex, age (continuous), race / ethnicity (non-Hispanic White, non-Hispanic Black, Mexican American or other), education (high school or higher vs. less than high school), body mass index (continuous), smoking (never, former, current), cotinine (continuous), menopausal status (yes, no), and use of vitamin / mineral supplements (yes, no). The odds for hypertension at the 10^th percentile (115 µg/L) of the serum selenium distribution were used as reference. The histogram shows the distribution of selenium concentrations in the study population.

Figure 3. Adjusted odds ratios (95% confidence intervals) for hypertension comparing the 90^th (160 µg/L) vs. the 10^th (115 µg/L) percentiles of the serum selenium distribution

Serum selenium was modeled as restricted quadratic splines with nodes at the 5^th, 50^th, and 95^th percentiles. Multivariable logistic regression models were adjusted for sex, age (continuous), race / ethnicity (non-Hispanic White, non-Hispanic Black, Mexican American or other), education (high school or higher vs. less than high school), body mass index (continuous), smoking (never, former, current), cotinine (continuous), menopausal status (yes, no), and use of vitamin / mineral supplements (yes, no). Separate models for every interaction were fitted, including all these covariables but each with interaction terms for the selenium splines and the variable of interest. The size of the square indicates the number of participants in each stratum.