Iron Status is Associated with Asthma and Lung Function in US Women

<div><p>Background</p><p>Asthma and iron deficiency are common conditions. Whether iron status affects the risk of asthma is unclear.</p><p>Objective</p><p>To determine the relationship between iron status and asthma, lung function, and pulmonary inflammation.</p><p>Methods</p><p>Relationships between measures of iron status (serum ferritin, serum soluble transferrin receptor (sTfR), and sTfR/log10ferritin (sTfR-F Index)) and asthma, lung function, and pulmonary inflammation were examined in women 20-49 years in the National Health and Nutrition Examination Survey. Logistic, linear, and quadratic regression models accounting for the survey design of NHANES were used to evaluate associations between iron status and asthma-related outcomes and were adjusted for race/ethnicity, age, smoking status, income, and BMI.</p><p>Results</p><p>Approximately 16% reported a lifetime history of asthma, 9% reported current asthma, and 5% reported a recent asthma episode/attack (n = 2906). Increased ferritin (iron stores) was associated with decreased odds of lifetime asthma, current asthma, and asthma attacks/episodes in the range of ferritin linearly correlated with iron stores (20-300ng/ml). The highest quintile of ferritin (>76 ng/ml) was also associated with a decreased odds of asthma. Ferritin levels were not associated with FEV1. Increased values of the sTfR-F Index and sTfR, indicating <i>lower</i> body iron and <i>higher</i> tissue iron need, respectively, were associated with decreased FEV1, but neither was associated with asthma. None of the iron indices were associated with FeNO.</p><p>Conclusion</p><p>In US women, higher <i>iron stores</i> were inversely associated with asthma and lower <i>body iron</i> and higher <i>tissue iron need</i> were associated with lower lung function. Together, these findings suggest that iron status may play a role in asthma and lung function in US women.</p></div

Predicted relationships between the full range of ferritin concentrations and asthma- related outcomes, generated from regression models: (a) lifetime asthma and (b) current asthma.

<p>95% confidence intervals are depicted by the shaded areas. Vertical line represents approximately 20ng/ml ferritin.</p

Population characteristics (n = 2906).

<p>All data posted as mean (SE) unless otherwise indicated. Geometric means are presented for all variables log-transformed in presented analyses.</p><p>*ferritin < 20ng/ml</p><p>SE = linearized standard error</p><p>^§n = 2678;</p><p>^†n = 2415;</p><p>^$n = 2378;</p><p>^‡n = 2444;</p><p>^ᶿn = 2374;</p><p>^ᶲn = 2470;</p><p>^λn = 2901</p><p>Population characteristics (n = 2906).</p

Relationships between iron status and asthma outcomes.

<p>*Adjusted for race/ethnicity, age, smoking, income, and BMI</p><p><b>Bolded</b> results are statistically significant, with p<0.05</p><p>^‡n = 2906 for unadjusted, n = 2663 for adjusted; ferritin Q1–4: 1.8–76.0ng/ml, Q5: >76.0ng/ml</p><p>^§Ferritin restricted to values from 20 to 300 ng/ml, inclusive; n = 2134 for unadjusted, n = 1963 for adjusted</p><p>^†n = 2901 for unadjusted, n = 2658 for adjusted</p><p>Relationships between iron status and asthma outcomes.</p

A pilot feeding study for adults with asthma: The healthy eating better breathing trial

<div><p>Rationale</p><p>Evidence from observational studies and to a lesser extent clinical trials suggest that a healthy diet may improve symptoms and lung function in patients with asthma. We conducted a pilot study to determine the feasibility of conducting a larger scale dietary trial and to provide preliminary evidence on the impact of a healthy diet on asthma outcomes.</p><p>Methods</p><p>In a randomized, two period cross-over trial, participants with asthma received a 4-week dietary intervention followed by a usual diet (or vice versa), separated by a 4-week washout. The dietary intervention was a healthy diet rich in unsaturated fat. During the dietary intervention, participants ate three meals per week on site at the Johns Hopkins ProHealth Research Center. All remaining meals and snacks were provided for participants to consume off-site. During the control diet, participants were instructed to continue their usual dietary intake. Relevant biomarkers and asthma clinical outcomes were assessed at 0, 2, and 4 weeks after starting each arm of the study.</p><p>Results</p><p>Eleven participants were randomized, and seven completed the full study protocol. Among these seven participants, average age was 42 years, six were female, and six were African American. Participant self-report of dietary intake revealed significant increases in fruit, vegetable, and omega-3 fatty acid intake with the dietary intervention compared to usual diet. Serum carotenoids (eg. lutein and beta-cryptoxanthin) increased in the intervention versus control. Total cholesterol decreased in the intervention versus control diet. There was no consistent effect on asthma outcomes.</p><p>Conclusions</p><p>The findings suggest that a feeding trial in participants with asthma is feasible. Larger trials are needed to definitively assess the potential benefits of dietary interventions on pulmonary symptoms and function in patients with asthma.</p></div

Participant-Reported dietary intake from 24 Hour dietary recalls.

<p>Participant-Reported dietary intake from 24 Hour dietary recalls.</p

Change in asthma morbidity outcomes.

<p>Change in asthma morbidity outcomes.</p

Participant characteristics.

<p>Participant characteristics.</p

Consort diagram.

<p>Participants screened and enrolled.</p

Select asthma morbidity outcomes.

<p>Data in each graph represent the change in value from week 0 to week 4 of the control diet and the change in value from week 0 to week 4 of the intervention diet. Points are linked by lines connecting responses within individual participants.</p