© 2005 American Thoracic Society
Anorexia Nervosa and EmphysemaTo the Editor:The conclusion of Dr. Coxson and colleagues in their recent article that " emphysema-like" or "early emphysema" changes in their patients were induced by anorexia nervosa is based on correlations between body mass index (BMI) and lung diffusing capacity (DL) and between BMI and DL and computed tomography (CT) scans of the lung (1). Because CT lung measurements were only recently described, and have not yet been validated by other studies, we limit our remarks to lung function results. Although the authors describe their control group as normal, the BMI of these subjects, according to NIH guidelines, place them in the overweight category, thus spuriously amplifying the difference between patients and "normal subjects." In agreement with our own results in subjects with anorexia (2), both spirometry and DL values were within normal limits in their patients and comparable to the values recorded in a control group, practically excluding the presence of emphysema. The authors report a significant correlation between BMI and predicted values of DL, but not between the absolute figures of DL and BMI. However, the r value was rather low (0.5), explaining only about a quarter of the variance. It is not clear why the authors consider that a rather weak correlation between BMI and DL is an argument for malnutrition-induced emphysema, but normal values for both spirometry and DL are not an argument against this hypothesis. Confounding factors can influence this correlation. For example, the authors also report, but without comment, a negative correlation between BMI and FEV1/FVC—that is, that curiously enough, an increase in BMI would be associated with a low FEV1/FVC. It must also be stressed that DL is not an indicator of early emphysema (3). The report by the authors of a single case of anorexia nervosa associated with bullae and a low DL cannot be considered an argument for their hypothesis. We have found (2), like others (4), decreased values for maximal inspiratory and expiratory pressure in our patients, a rather direct reflection of malnutrition. Coxson and coworkers report normal values for these indices (1). However, predicted values were not reported (there is a wide range of predicted values), and maximal pressures were not measured in their control group. Finally, the study (5) done in subjects who died in the Warsaw Ghetto during World War II, suggesting that death from starvation was associated with emphysema, should be considered with caution because it was done before criteria for pathologic diagnosis of emphysema were available.
University of Louvain Medical School, Brussels, Belgium FOOTNOTES Conflict of Interest Statement: D.S. does not have a financial relationship with a commercial entity that has an interest in the subject of this letter; T.P. does not have a financial relationship with a commercial entity that has an interest in the subject of this letter. REFERENCES
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