# Iron status in women of reproductive age in Switzerland: the role of inflammation and ferritin thresholds for the prevalence of iron deficiency–a cross-sectional study

## TL;DR

This study finds that nearly 20% of young Swiss women are iron deficient, with a clear threshold for when iron deficiency affects red blood cell production.

## Contribution

The study identifies a ferritin threshold of 28.5 µg/l for impaired erythropoiesis and shows that inflammation corrections are unnecessary in low-inflammation populations.

## Key findings

- 18.9% of women were iron deficient, with 4.7% being anemic and 3.3% iron-deficient anemic.
- Ferritin levels below 28.5 µg/l correlate with a decline in hemoglobin, indicating impaired erythropoiesis.
- Inflammation had a negligible effect on iron deficiency prevalence in this low-inflammation population.

## Abstract

Iron deficiency in women of childbearing age remains a public health challenge, but prevalence data in high-income countries is scarce and the role of predictors remains uncertain. We determined the prevalence of iron deficiency in women in Switzerland and assessed the influence of BMI, inflammation, and age on iron status. In addition, we determined the ferritin concentration below which hemoglobin (Hb) starts to decline.

This is a secondary, pooled data analysis including data from 26 studies conducted in Switzerland between 2009 and 2020. Participants were a convenience sample of generally healthy women aged between 18 and 54 years (n = 2709).

The prevalence of iron deficiency in women (median 23.3 years; IQR: 21.1–26.4) was 18.9%, while 4.7% of the women were anemic and 3.3% were iron deficient anemic. The prevalence of overweight (BMI ≥ 25 kg/m2) was 7.2%, and 1.4% were obese (BMI ≥ 30 kg/m2); 8.9% suffered from acute inflammation (CRP ≥ 5 mg/l). In multivariate regression analysis, BMI and age were positive predictors of ferritin (p < 0.001), while inflammation was not. Correcting iron status for inflammation had a negligible effect on the prevalence of iron deficiency. We observed a decrease in Hb below a ferritin concentration of 28.5 µg/l.

In this convenience sample of young women in Switzerland, one in five was iron deficient and one in 30 was anemic due to iron deficiency. Controlling ferritin concentrations for inflammation did not substantially affect the prevalence of iron deficiency, indicating that such corrections are redundant in a healthy population with a low prevalence of inflammation. Impaired erythropoiesis was observed when the ferritin concentration fell below 28.5 µg/l, providing further evidence for a physiologically based ferritin threshold to identify the onset of iron-deficient erythropoiesis.