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P.J. Safarik University, Kosice, Slovakia
Correspondence to: Ruzena, Tkacova, MD, PhD, L. Pasteur Teaching Hospital, Medical Faculty, P.J. Safarik University, Department of Respiratory Medicine, Rastislavova 43, Kosice 041 90, Slovakia; e-mail: rtkacova{at}central.medic.upjs.sk
To the Editor:
We read with interest the article in CHEST (October 2005)1 by de Torres et al in which the authors compared 53 FEV1-matched men and women, and found that women were younger, had better oxygenation, fewer comorbidities, poorer quality of life, and higher degree of dyspnea than men. However, since only 8% of patients had stage IV COPD,1 a question remains regarding gender differences in patients with the most severe disease. Therefore, readers may be interested in a similar analysis that we conducted among patients with very severe COPD.
We studied 189 COPD patients (154 men and 35 women) with chronic respiratory insufficiency meeting the indication criteria for long-term oxygen therapy (LTOT). At the time of LTOT initiation, no age differences were seen between men and women (mean [± SD] age, 67 ± 8 vs 69 ± 9 years, respectively). Whereas FEV1 did not differ between men and women, women had significantly lower FVC and TLC, and higher FEV1/FVC compared to men (Table 1 ). No gender differences were seen in arterial blood gases or nutritional status. The proportion of men and women with comorbid conditions was similar: arterial hypertension, 38% vs 50%, respectively; diabetes, 19% vs 13%, respectively; myocardial infarction, 18% vs 7%, respectively; and stroke, 6% vs 3%, respectively.
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* Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz, Tenerife, Spain* Caritas St. Elizabeth Health System, Boston, MA
Correspondence to: Juan P. de Torres, MD, Unidad de Investigación Hospital Nuestra Señora de Candelaria, Carretera del Rosario s/n, Santa Cruz, Tenerife, Spain 38010; e-mail: jupa65{at}hotmail.com
To the Editor:
We are pleased that Tkacova et al found our work (October 2005)1 interesting. As we pointed out, our findings are only applicable to the population included in our study sample (ie, women with mild-to-moderate COPD from the outpatient clinic at University Hospital clinic). The findings in a population of women and men requiring oxygen, as reported by Tkacova and coworkers, represent an even more selected group in whom the final expression of the disease may be due to many other phenotypic and mechanistic issues that cannot be extrapolated to patients without significant hypoxemia.
Indeed, the data presented in that letter refer to a population of COPD patients with an uneven number of patients in both gender groups (154 men and 35 women) with similar degrees of airway obstruction (mean [± SD] FEV1, 39 ± 19% predicted) and, by definition, a similar degree of hypoxemia at the time of the initiation of long-term oxygen therapy (LTOT). By forcing both factors to be similar, it is not surprising that men and women had the same age, similar degrees of comorbidity, equal PaO2-PaCO2 values, and the same body mass indexes. When we analyzed our database and evaluated only those patients in Global Initiative for Chronic Obstructive Lung Disease stages III and IV (28 men and 28 women) with exactly the same mean FEV1 (40 ± 7% predicted), we still observed differences in the studied prognostic parameters (ie, men vs women), as follows: mean age, 64 ± 7 vs 59 ± 11 years (p < 0.05); mean modified Medical Research Council score of 
2, 11% vs 64%, respectively (p < 0.05); mean body mass index, 27 ± 3 vs 23 ± 3, respectively (p < 0.05); mean PaO2, 64 ± 10 vs 72 ± 11 mm Hg, respectively (p < 0.05); mean PaCO2, 46 ± 6 vs 40 ± 5 mm Hg, respectively (p < 0.05); mean 6-min walk distance, 99 ± 20 vs 84 ± 21% predicted, respectively (p < 0.005); and mean Charlson scale, 4 (range, 3 to 8) vs 2 (range, 1 to 3) [p < 0.05]. We did not find differences in functional residual capacity percent predicted and all domains of the St. George Respiratory Questionnaire.
The differences between our findings and those of Tkacova et al could be explained in part by the more natural heterogeneity of the disease in our patients compared to the more homogeneous population reported by those authors. We may speculate that when our women reach the need for LTOT they will be older and probably will have more comorbidities. This may explain partially the data indicating that women receiving LTOT live longer that their male counterparts.2 Actually, we believe the findings of Tkacova et al are complementary to ours. Taken together, both sets of data suggest that COPD runs for a longer symptomatic period in women since the women in our study expressed worse dyspnea, exercise capacity, and quality of life at earlier stages. However, as the disease progresses these gender differences could disappear, and, by the time some of the patients need oxygen, the gender differences may no longer exist.
The most important issue is to begin to address the gender differences in the expression of the disease, since in the year 2000 for the first time more women than men died of COPD in the United States.3 We believe that data like these from Tkacova et al are desperately needed and welcomed so that we can increase our knowledge of this dreadful epidemic.
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