Hemoglobin concentrations in 358 apparently healthy 80-year-old Danish men and women. Should the reference interval be adjusted for age?

Background and aims: In elderly Danes, reference intervals for hemoglobin (Hb) concentrations are derived from younger population groups. The aim was to examine reference intervals for Hb and cut-off limits for anemia by application of criteria for normality to a representative population of 80-year-olds. Methods: Participants in this epidemiological health survey cohort were 358 subjects (171 men) 80 years of age. A dietary survey was performed in 232 subjects. Blood samples included Hb, red cell indices, serum ferritin, serum C-reactive protein, renal and hepatic function tests. Normality criteria for Hb were: 1) values in all participants; 2) values in apparently healthy subjects; 3) values in 10-year survivors. Hb was compared with muscle strength, physical performance and diet. Results: In the entire series, median Hb was 140 g/L, 5-95 percentile 116-160 g/L in men, and 131 g/L, 5-95 percentile 114-147 g/L in women (p<0.001). The prevalence of anemia, as defined by World Health Organization (WHO) criteria, was 18% in men and 17% in women. Apparently healthy iron-replete men (n=129) and women (n=141) had median Hb of 141 g/L and 131 g/L. Median Hb levels were higher in 10-year surviving men (143 g/L) than in deceased men (139 g/L whereas surviving and deceased women had similar median Hb (131 g/L). Hb and muscle strength were significantly correlated. Subjects with physical performance score >= 20 had a lower frequency of anemia. There was no correlation between Hb and dietary or supplemental iron intake. In men, Hb was correlated to meat consumption. Conclusions: WHO decision limits for anemia should not be lowered in 80-year-old subjects. "Optimal" Hb concentrations with respect to survival appear to be at least 140 g/L in men and 131 g/L in women. Further research should evaluate whether not only treating anemia, but also increasing Hb by using erythropoietin and hematinics, may improve functional status and survival in the elderly.