Multiple Micronutrient Deficiencies Exist in Aged‐care Residents, with Serum Zinc, not Iron, Being a Major Predictor of Anemia
Authors: MacDonell Sue , Miller Jody , Harper Michelle , Reid Malcolm , Haszard Jill , Gibson Rosalind , Houghton Lisa 
Published: November 2023

Background

Anemia is a significant comorbidity in older adults with a complex etiology that is not fully attributable to iron deficiency. Other micronutrient and non‐nutritional health‐related associations have also been implicated as possible causal factors.

Objective

To examine the relations of serum iron, zinc, selenium and vitamin D status with hemoglobin concentrations and anemia in residents of New Zealand aged‐care facilities.

Methods

A cross‐sectional survey of 309 rest‐home level care residents from 16 aged‐care facilities across New Zealand. Blood samples were analyzed for biomarkers of micronutrient status and inflammation. Multivariate regression was performed to examine the relations of micronutrient and inflammation biomarkers, and socio‐demographic and health factors (BMI, medication use, malnutrition and frailty status), with hemoglobin and anemia. Direct and indirect (through zinc) associations between selenium and hemoglobin were investigated using mediation analysis.

Results

Data were available for 284 residents with complete hemoglobin and micronutrient results. Mean participant age was 85.1 (± 7.7) years old and approximately two‐thirds were female (67.6%). Anemia was present in 89 participants (31.3%) however, less than 2% of participants had either depleted iron stores or iron deficiency (with or without the presence of anemia). In contrast, 81.7% and 50.7% of participants had low serum zinc (< 10.7 μmol/L) and low serum selenium concentrations (< 0.82 μmol/L), respectively. Vitamin D deficiency (25OHD < 50 nmol/L) was low, as 75% of all residents were taking monthly high‐dose vitamin D supplements. Proton pump inhibitor (PPI) or H2 antagonist medications were prescribed for 47.4% of participants. Being female, taking PPI or H2 antagonist medications and having a BMI ≥ 30kg/m2 were negatively associated with hemoglobin, while there was a positive association with serum zinc (P < 0.05). Selenium had an indirect effect on hemoglobin which was mediated by zinc, with a significant effect of selenium on zinc and zinc on hemoglobin (P < 0.05). The effect of zinc explained 30.1% of the relationship between serum selenium and hemoglobin. Low serum zinc, PPI or H2 antagonist medications and risk of malnutrition were associated with greater odds of being anemic (P < 0.05).

Conclusion

High prevalence of low serum zinc is associated with a greater risk of anemia in elderly aged care residents, and mediates the effect of selenium on hemoglobin. Medications which alter iron absorption are also associated with lower hemoglobin concentrations. These findings emphasize the importance of monitoring the effect of medication on nutritional status in this vulnerable population and consideration of multiple micronutrient deficiencies when interpreting anemia.

Support or Funding Information

Department of Human Nutrition, University of Otago; The Maurice and Phyllis Paykel Trust, New Zealand; Lottery Health New Zealand