Selenium status in a 12 month longitudinal study of older Tasmanian adults

Background: Selenium is important in many areas of health including immune and antioxidant function. Inadequate selenium status in the elderly is common, and may be particularly important as immune function decreases and risk of chronic and other disease increases. Little data has been reported about medium term variation in selenium status. Objectives: To investigate the magnitude of variation in selenium status of older adults over 12 months and the influence of season. Design: A 12 month longitudinal study. Setting: Independent, community dwelling self-selected older adults in 2009 and 2010. Participants: 80 adults (23 men, 57 women) in Australia, aged 60 years or older. Measurements: Dietary selenium intake was assessed using a food frequency questionnaire. Serum selenium concentration was measured using graphite furnace atomic absorption spectroscopy. Results: At commencement, men consumed 80.6 μg, and women 66.8 μg selenium per day, respectively; there was however, no significant difference in serum selenium (1.11 v. 1.09 μmol/l; P = 0.58). Repeated measures nonlinear regression analysis revealed the mean magnitude of variation over 12 months was small and non-significant (0.02 μmol/l; 95% CI -0.01 to 0.05; P = 0.17). Overall there was minimal variation over the study period; greatest variation was observed in subjects in the upper quartile of selenium status at commencement; the mean SD of serum selenium change compared to all others was 0.15 vs. 0.07 μmol/l (95% CI of difference 0.04 to 0.13; P<0.001). Conclusions: In these older adults, selenium status did not vary significantly over 12 months and there was no evidence of a seasonal pattern.