CHICAGO — A small but provocative Italian study suggests that women complaining of chronic idiopathic cough should be evaluated for iron deficiency.
Researchers at the University of Turin (Italy) observed that cough and signs and symptoms of pharyngolaryngitis were improved or resolved after iron supplementation in 16 healthy nonsmoking women who had idiopathic cough and iron deficiency (average serum ferritin 9.4 ng/mL) and mild anemia (hemoglobin 11.6 g/dL).
The women, aged 18–56 years, had no history of atopy, asthma, or other bronchopulmonary diseases, and no evidence of gastroesophageal reflux. All had normal results on lung function tests, lead investigator Dr. Caterina B. Bucca reported at the annual meeting of the American College of Chest Physicians.
The women presented with marked oral redness and soreness, atrophy of oral mucosa and tongue papillae, and angular cheilosis. Nine patients had dysphonia. Exhaled nitric oxide was normal (average 14.9 parts per billion) in all patients.
Histamine challenge showed bronchial hyperresponsiveness in 4 women, extrathoracic airway hyperresponsiveness in 14 women, and cough hyperresponsiveness in 15 women. A significant association was observed between PC5 coughs (the histamine concentration that provokes five coughs) and PC25 MIF50 (provocative concentration causing a greater than 25% fall in maximal midinspiratory flow at 50% of vital capacity), reported Dr. Bucca of the department of biomedical sciences and human oncology at the University of Turin. After iron supplementation, signs and symptoms of pharyngolaryngitis were resolved in 10 women and improved in 6 women. Significant increases were observed in PC20 FEV1 (provocative concentration causing a 20% drop in forced expiratory volume in 1 second): 18.8 mg/mL to 24.1 mg/mL; significant increases were also seen in PC25 MIF50 (6.2 mg/mL to 22.2 mg/mL) and in PC5 coughs (3.8 mg/mL to 17.8 mg/mL).
Dr. Bucca suggested that the tentative explanation of how iron deficiency causes cough is based on the knowledge that iron deficiency impairs immunologic defenses and induces the release of inflammatory cytokines.
“This leads to damage of the airway mucosa, which becomes more permeable to noxious stimuli so that the nervous receptors responsible for the onset of cough are more easily reached by irritants,” Dr. Bucca said in an interview. “Infections of the pharynx and larynx are also favored so that cough is often associated with painful and inflamed throat and with dysphonia.”
Iron deficiency is present in 20% of women in industrialized countries, and in the United States nearly one-third of women have virtually no iron stores. Cough is also more frequent in women than in men.
Dr. Bucca is currently evaluating the nutritional status of all patients who present to her clinic for chronic cough, either idiopathic or associated with diseases of the upper airway, and is planning an epidemiologic study to assess the prevalence of cough and iron deficiency in women of childbearing age.