May 17, 2010 (New Orleans, Louisiana) — Regular long-term use of vitamin E supplementation might protect women against the development of chronic lung disease, according to a secondary analysis of the large Women's Health Study. The findings were presented here at the American Thoracic Society (ATS) 2010 International Conference by investigators from Cornell University in Ithaca, New York, and Brigham and Women's Hospital in Boston, Massachusetts.
"Vitamin E supplementation reduced the risk of new chronic lung disease diagnoses by 10% after 10 years of use," reported Anne Hermetet Agler, a doctoral candidate at Cornell's Division of Nutritional Sciences. Although observational studies have examined the protective effects of vitamin E, she said, this is "the first definitive report specifically for an effect of vitamin E in prevention."
The study randomized 39,876 female healthcare professionals to receive 600 IU of vitamin E or placebo (±100 mg aspirin) for a mean of 9.8 years. After excluding patients with chronic lung disease at baseline, the final analysis included 19,299 women in the vitamin E group and 19,298 in the placebo group.
The primary end point was a reduction in chronic lung disease, defined as chronic bronchitis, emphysema, or bronchiectasis.
Because the baseline characteristics were well matched between the groups, Ms. Agler reported, "we can be certain that what we are seeing is the effect of vitamin E."
The oxidant/antioxidant balance in lung tissue is thought to contribute to the risk for chronic obstructive pulmonary disease (COPD). Previous observational studies have shown that higher antioxidant status is associated with a lower risk for COPD, but most such studies were conducted only in men and looked only at a reduction in symptoms.
"We wanted to see if vitamin E could actually prevent COPD in a large population," she told journalists at a press briefing held during the ATS proceedings.
The study identified 760 new reports of chronic lung disease in the vitamin E group and 846 new cases in the placebo group (hazard ratio, 0.90; 95% confidence interval [CI], 0.81 - 0.99; P = .03).
The difference was significant after adjustment for cigarette smoking, aspirin assignment, randomization age, multivitamin use, body mass index, preexisting asthma, diabetes, hypercholesterolemia, hypertension, inflammatory disease, and dietary intake of vitamin C or nonstudy-assigned vitamin E.
"We saw no change in the effect of vitamin E [after adjustment], which was quite robust," Ms. Agler said.
According to the investigators, the study has "face validity" based on the fact that smoking was shown to be a strong predictor of chronic lung disease risk, with current smokers demonstrating a 4-fold increased risk over never-smokers (95% CI, 3.70 - 4.70; P < .001). The researchers also evaluated the effects of self-reported physician diagnosis of asthma on incidence, and found no significant association.
She explained that as lung disease develops, tissue damage occurs through several proposed processes, including inflammation and exposure to free radicals. "Vitamin E may protect the lung against this kind of damage," she said.
The investigators further believe that part of the process might stem from the transport of vitamin E by high-density lipoprotein (HDL) into the lung. Because women have higher HDL levels than men, if this concept is correct, men might not enjoy the same protection from vitamin E, she suggested. Studies are currently underway to evaluate the effect of vitamin E on chronic lung disease in men.
Currently, the investigators are not ready to recommend widespread adoption of vitamin E for the prevention of chronic lung disease on the basis of these findings alone, because very high doses of vitamin E have been associated with congestive heart failure and increased all-cause mortality in other studies, she noted.
Richard Casaburi, MD, PhD, professor of medicine at the UCLA School of Medicine, in Los Angeles, California, moderated the press briefing and commented on the study. "I think this study has been done well. We are entering a time of big COPD trials, and this is a very impressive interventional study. But I do agree," he added, "that we are not ready to prescribe vitamin E based on just these findings."
Dr. Casaburi suggested that the ideal measurement of outcome should involve spirometry, not self-report, and he would like to see this in confirmatory studies, but he added that "in a blinded trial [such as this one], even a subjective outcome should be valid."
Ms. Agler agreed and pointed out that the study's subjects were healthcare professionals who, as a group, have been shown to give fairly reliable self-reports.
Ms. Agler and Dr. Casaburi have disclosed no relevant financial relationships.
American Thoracic Society (ATS) 2010 International Conference: Abstract A5183. Presented May 15, 2010
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