A 12 month longitudinal study of selenium status in older Tasmanian adults

Selenium is known to be important in many areas of health, including the immune system and in antioxidant function. Suboptimal selenium status in the elderly appears common, and this may be particularly important as immune function decreases and risk of chronic and other disease increases. Few medium-term longitudinal studies of selenium status have been reported. Objective To determine the magnitude of variation in selenium status over 12 months in older adults, in a population which many have marginal selenium status. Design A 12 month longitudinal, observational study of selenium status was conducted in older Tasmanians. Twenty three men and 57 women (mean age 69.6 yrs) were studied repeatedly at 3 month intervals over 12 months; selenium status was assessed by measuring dietary intake using a semi-quantitative food frequency questionnaire and serum selenium concentration using graphite furnace atomic absorption spectroscopy. Outcomes At baseline, men consumed 80.6 Pg, and women 62.9 Pg selenium per day, respectively; there was however no significant difference in serum selenium (1.11 v. 1.09 Pmol/l; P=0.58). Overall, 50 participants (62.5%) had baseline serum selenium below 1.14 Pmol/l, a level considered to represent the physiological requirement of selenium. Repeated measures nonlinear regression analysis revealed the mean magnitude of variation over 12 months was small and non-significant (0.02 Pmol/l; 95% CI -0.01 to 0.05; P=0.17). Only dietary intake after 9 months and serum selenium after 12 months were significantly different to other time points when compared using repeated measures linear regression. While overall there was minimal variation observed, subjects in the upper quartile of selenium status at baseline appeared to experience greater variation in selenium status over the study period. Conclusion In this cohort of older adults, selenium status did not vary significantly over 12 months and there was no evidence of a seasonal pattern. Source of funding Supported by the Clifford Craig Medical Research Trust, Launceston, Tasmania