Thyroid function and anemia: results from the Brazilian Longitudinal Study of Adult Health

The aim of this study was to analyze the association of thyroid stimulating hormone and free-thyroxin with anemia as well as the role of several sociodemographic variables in these associations.

This is a cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health study (2008-2010), a prospective cohort study of civil servants in six locations in Brazil. Inclusion criteria: to be an active or retired civil servant of one of the institutions and 35-74 years at enrollment. Exclusion criteria: pregnancy less than 4 months before entering the study for women, intention to quit the institution soon, live outside the metropolitan region where the investigation center is located or communication problems. Anemia was defined as hemoglobin <12 g% in women and <13 g% in men. After exclusions, 13,247 participants were included in the analysis. Models were presented without adjustment and adjusted for sociodemographic and clinical risk factors. The study was approved by the Ethic Committee.

Median age was 51.9 (51-53 years), 54% of women There was an association of less presence of anemia with higher free-thyroxin levels considering the entire sample: OR 0.80 (95%CI 0.65-0.98) for the second quintile; OR 0.55 (95%CI 0.43-0.70) for third quintile; OR 0.49 (95%CI 0.38-0.63) for fourth quintile; and OR 0.52 (95%CI 0.40-0.66) for fifth quintile for free-thyroxin levels. This association was also present when analyzing the sample by sex.

Higher levels of free-thyroxin are associated with lower odds of anemia. No associations were found between thyroid stimulating hormone levels and anemia. In analysis, according to sex, No differences were found between men and women.