Looking at the relationship between hemoglobin concentration and prevalent mobility difficulty in older women. Should the criteria currently used to define anemia in older people be reevaluated?

OBJECTIVES: The World Health Organization (WHO) and other currently used criteria for defining anemia in older women are mainly based on statistical distribution considerations. To explore their clinical appropriateness, we evaluated the relationship between hemoglobin (Hb) concentration, prevalent mobility difficulty, and the Summary Performance Score (SPS). DESIGN: Cross-sectional study. SETTING: Two population-based studies, the Women's Health and Aging Studies I and II, Baltimore, Maryland. PARTICIPANTS: Six hundred thirty-three community-dwelling women aged 70 to 80 with Hb levels obtained within 90 days from baseline assessment, MEASUREMENTS: Mobility difficulty (self-reported difficulty walking one-quarter of a mile or climbing 10 steps (primary outcome)). SPS, a performance-based summary measure of lower extremity function that combines the results of walking, chair stands, and balance tests (secondary outcome). RESULTS: Mobility difficulty prevalence was not constant within the WHO "normal" Hb range (12.0-16.0 g/dL). For example, a Hb of 13.5 g/dL was associated with a significantly lower mobility difficulty prevalence than a Hb of 12.0 g/dL (OR = 0.68, 95% Cl = 0.47-0.93), even after adjustment for chronic diseases and other relevant health indicators. A consistent trend of improvement in performance-based scores with increasing Hb categories less than 12.0 g/dL, 12.0 to 13.0 g/dL, and 13.0-14.0 g/dL was observed. CONCLUSION: Our findings raise two hypotheses: (1) Hb currently perceived as "mildly-low" and even "low-normal" might have an independent, adverse effect on mobility function, and (2) Hb of 12.0 g/dL might be a suboptimal criterion for defining anemia in older women. Formal testing of these hypotheses might prove relevant for anemia- and mobility disability-related clinical decision-making.