In a large cross-sectional study of survey data from U.S. youth under age 17, increases in the antioxidants serum beta-carotene and vitamin C, along with the trace mineral selenium which is also considered an antioxidant, were associated with a lower risk of asthma prevalence. Even stronger asthma reduction associations for the three antioxidants were found in subgroups of young people exposed to passive smoke. The researchers studied data from 6,153 young persons from 4 to 16 years old who were a part of the Third National Health and Nutrition Survey (NHAMES III). A household youth questionnaire, answered usually by the mother, was used for participants less than 17 years old. The study included a comprehensive health examination, together with various laboratory measurements. Using separate antioxidant models, the researchers said that serum vitamin E had little or no association with asthma. However, a standard deviation increase in beta-carotene was associated with a 10 percent reduction in asthma prevalence in those not exposed to smoke and a 40 percent reduction in young persons who had passive smoke exposure. The pattern for vitamin C was similar to beta-carotene results, according to the researchers. An increase in selenium was associated with a 10 to 20 percent decrease in asthma prevalence. In youth with passive smoke exposure, investigators found a 50 percent reduction in asthma prevalence associated with selenium. (In the diet, a high percentage of the trace element selenium is found in cereal grains, fish, meat, and poultry. Toxic effects have been reported among individuals who consumed excessive selenium supplements.) The study appears in the first issue for February 2004 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.
AIRWAY INFLAMMATION PRESENT YEARS AFTER CAUSATIVE AGENT FOR OCCUPATIONAL ASTHMA GONE
A new study shows that airway inflammation is present in persons with occupational asthma years after their exposure to the provoking agent has been eliminated, suggesting that the residual effects are the cause of persistent airway hyperresponsiveness and asthmatic symptoms. Canadian investigators presented data for 103 subjects with occupational asthma 8 years after their exposure ceased. The persons involved in the test were separated into three groups, with 28 classified as "cured," 44 subjects "improved," and 31 "not improved." The classifications were based on their individual responses to a questionnaire, results from induced sputum samples, and an airway challenge test. Of the 103 subjects, the researchers were only able to obtain satisfactory samples of individual sputum from 98 persons with occupational asthma to determine the number of sputum eosinophils and neutrophils that were present. Higher levels of both types of cells are associated with bronchial hyperresponsiveness. The investigators said that one-third of the uncured subjects, twice the number of subjects who were cured or improved, had significant eosinophilia present and even large numbers of neutrophilia. They found the presence of airway inflammation in the uncured group "puzzling," since the individuals were no longer exposed to the agent causing occupational asthma. The study appears in the first issue for February 2004 of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.
IMPROVED FUNCTION IN CONGESTIVE HEART FAILURE PATIENTS WITH SLEEP APNEA
Researchers demonstrated that continuous positive airway pressure (CPAP) for moderately obstructive sleep apnea in patients who had congestive heart failure helped to improve systolic heart function, reduce oxygen deficiency in the blood, lessen sympathetic nerve activity, and enhance the quality of life. The Australian investigators showed significant improvements over 3 months in 19 patients in the CPAP-treated group, as contrasted with 21 control patients who did not receive the treatment. (Congestive heart failure (CHF) occurs when the heart does not pump enough blood to meet the body's normal requirements for oxygen and nutrients. One-year mortality from CHF is 25 to 30 percent. Several earlier clinical studies suggested that the prevalence of sleep-disordered breathing in CHF was 50 to 60 percent.) In the 19 treated patients who completed the study, CPAP treatment was associated with a 5 percent increase in left- ventricular ejection fraction, a key symptom. In addition, the treatment reduced levels of overnight urinary norepinephrine (a heart stimulant) and improved the patients' quality of life. It did not reduce either dyspnea (severe breathlessness which is a serious handicap in CHF) or exercise capacity. The investigators point out that the improvement in left-ventricular function in their study was similar to or greater than other large CHF pharmacologic intervention trials that have shown important mortality improvements. They believe that their results represent an advance in the treatment of patients with CHF. The study appears in the first issue for February 2004 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.
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Journal
American Journal of Respiratory and Critical Care Medicine