Free thyroxine (FT4) and anemia in relation to drinking status of Japanese men: the Nagasaki islands study.

It is well known that hypothyroidism is associated with anemia. It has also been reported that alcohol consumption may affect thyroid function. Furthermore, hemoglobin levels of drinkers are reportedly higher than those of non-drinkers. However, no published study has investigated the association between thyroid function evaluated with the free thyroxine (FT4) test and anemia while taking drinking status into account. We conducted a cross-sectional study of 843 men aged 30-89 years undergoing general health checks. While no significant associations were noted between FT4 and anemia for total subjects, when the analysis was limited to non-drinkers, a significant association was observed. After adjustment for classical cardiovascular risk factors and thyroid stimulating hormones (TSH), adjusted odds ratio (OR) and 95% confidence interval (CI) for an increment of 1SD (standard deviation) for FT4 (0.17 ng/dL) for anemia were 0.85 (0.67-1.09) for total subjects, 0.59 (0.41-0.85) for non-drinkers, and 1.23 (0.83-1.83) for drinkers. In conclusion, FT4 is inversely associated with anemia for non-drinking but not for drinking men. However, drinking may act as a confounding factor for this association.