Prevalence of 25-hydroxyvitamin D deficiency in subgroups of elderly persons with anemia: association with anemia of inflammation.

Anemia and vitamin D deficiency are conditions that both result in significant morbidity and increase with age. The potential relationship between them remains poorly understood, particularly in the elderly. We used the Third National Health and Nutrition Examination Survey to examine the association of vitamin D deficiency with anemia subtypes in persons aged ≥ 60 years. Vitamin D deficiency was defined as serum levels < 20 ng/mL, and anemia was defined according to World Health Organization criteria. Vitamin D deficiency was associated with anemia prevalence independent of age, sex, or race/ethnicity (odds ratio, 1.47; 95% confidence interval, 1.06-2.05; P = .02) and varied significantly by anemia subtype (P overall = .003). The prevalence of vitamin D deficiency was 33.3% in the nonanemic population, 56% in anemia of inflammation (AI; P = .008), and 33.0% in unexplained anemia (P = .55). Non-Hispanic blacks had a 7-fold increased risk of AI compared with whites, and this was partially attenuated after adjusting for vitamin D deficiency. These data show that vitamin D deficiency is associated with specific subtypes of anemia in the elderly, especially in those with AI. Vitamin D may suppress inflammatory pathways, and studies to determine whether vitamin D supplementation ameliorates AI are warranted.