Study finds active vitamin D is associated with hemoglobin levels in older men

Posted on: February 10, 2015   by  Will Hunter

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Increasing evidence suggests that anemia is common in older people and may increase morbidity and mortality rates in this population. Anemia is a decrease in the amount of red blood cells or the amount of hemoglobin, the protein that carries oxygen throughout the body, in the blood. Symptoms of anemia include, fatigue, weakness, shortness of breath, and poor ability to exercise.

Globally, 20% of individuals 85 years and older suffer from anemia. In older populations, one-third of anemia cases is due to nutritional deficiency, one-third is due inflammation or chronic disease, and the other third of cases do have an explained cause.

Vitamin D deficiency is also common in older people due to impaired production of vitamin D in the skin and a lack of sun exposure, among other reasons.

There is some limited evidence that shows vitamin D is associated with anemia among community-dwelling older people, however the relationship between activated vitamin D and anemia has not been looked out any community-dwelling population group.

Circulating vitamin D is the standard and most reliable biomarker for determining vitamin D status. However, activated vitamin D is the form of vitamin D that is responsible for the all the beneficial effects of the hormone and conversion of circulating vitamin D to activated vitamin D in the kidneys is a process that declines with age.

Activated vitamin D regulates, along with other molecules, erythropoiesis, which is the process by which red blood cells are produced within the red bone marrow.

Therefore, researchers decided to analyze the relationship between both circulating vitamin D and activated vitamin D and hemoglobin levels in an older community.

To conduct the study, they retrieved data from 1570 participants enrolled in the Concord Health and Ageing in Men Project (CHAMP). CHAMP is an epidemiological study of a wide range of health issues in Australian men aged 70 years or older that began in 2005.

Baseline circulating vitamin D, activated vitamin D, and hemoglobin measurements were taken during 2005 and 2007. Two-year follow-up measurements were taken in 2007 and 2009, and five-year follow-up measurements were taken between 2012 and 2013.

They then performed a cross-sectional analysis of the baseline data and found the following:

  • Anemia was present in 14% of the men.
  • Men with anemia had significantly lower circulating and activated vitamin D compared to men without anemia.
  • Circulating vitamin D was positively associated with anemia (p = 0.01), however this relationship was no longer significant after adjustment for confounding variables.
  • Activated vitamin D was positively associated with anemia and the relationship (p<0.0001) remained significant after adjustment (p=0.003).

Using the follow-up data, they then performed a longitudinal analysis to determine how circulating and activated vitamin D was associated with hemoglobin over time. Here is what they found:

  • Circulating vitamin D level as baseline was not associated with changes in hemoglobin over time in either unadjusted or adjusted analyses.
  • Baseline activated vitamin D level was associated with changes in hemoglobin over two and five years in both unadjusted and adjusted analyses (p<0.0001).

These findings provide evidence that activated vitamin D plays a role in the development and progression of anemia. The evidence is strengthened by the fact that both the cross-sectional analysis and longitudinal analyses found similar findings.

The researchers summarized the results by saying,

“Serum 1,25D, but not 25D, concentrations are independently associated with haemoglobin levels in older men in both cross-sectional and longitudinal analyses. This raises the question whether vitamin D metabolites may influence anaemia states, mediated through different biological pathways, or represent a time-dependent biomarker of chronic ill health.”

The study’s strengths include a large, representative sample of community-dwelling Australian men. The researchers were also able to control for a large amount of confounders.

Limitations included a lack of dietary vitamin D intake measurements as well as data on times spent outdoors and sunscreen use.

Source

Hirani, V. et al. Cross-sectional and longitudinal associations between the active vitamin D metabolite (1,25 dihydroxyvitamin D) and haemoglobin levels in older Australian men: the Concord Health and Ageing in Men Project. Age, 2015.

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