Gender disparities in the functional significance of anemia among apparently healthy adults

Background: Data on the functional impact of anemia on cardiorespiratory fitness (CRF) and survival in healthy individuals are limited. Our aim was to evaluate the association between anemia thresholds, low CRF, and survival in otherwise healthy adults. Methods: Study population included 16 334 apparently healthy subjects attending annual periodic health screening examinations (71 200 annual visits), including exercise stress testing (EST). Anemia was defined by the World Health Organization (WHO) or Beutler and Waalens’ (BW) criteria. Low CRF was defined as the lowest fitness quintile according to the Bruce protocol. Results: The mean age was 46±10 years, and 70% were men. Mean Hb levels were 13±1 and 15±1 among women and men, respectively, with higher proportion of anemia among women. The majority of anemic subjects had mild anemia. When analyzing repeated annual visits, anemia was associated with a significant 39% and 64% increased risk of low CRF according the WHO and BW criteria only in women (n=18 672). Baseline anemia at first visit was associated with 2.6- and 1.9-fold increased risk of all-cause mortality using the WHO and BW criteria, exclusively in men (n=11 511). Conclusions: Overall, the functional and prognostic impact of anemia is gender dependent, based on the WHO and BW arbitrary criteria, suggesting differing mechanism and responses.