Six-minute walking distance in women with COPD

The 6-minute walk distance (6MWD) has been useful in the evaluation of men with COPD. Little is known about 6MWD in women with the disease.

Using healthy women as a reference, to evaluate the factors that help determine 6MWD in women with COPD. To explore if the 350 meters threshold differentiates survival in women as it does in men.

Healthy women (n = 164) and with COPD (n = 223) were included in the study. Age, pack-years history, smoking status, comorbidities (Charlson Index), BMI, MRC dyspnea, spirometry and 6MWD were recorded in all participants and PaO(2) and IC/TLC in COPD women. The patients were prospectively followed and deaths registered. Factors predicting 6MWD were determined by multiple regression analysis. ROC analysis was used to calculate the best threshold value for the 6MWD with mortality as gold standard. Kaplan-Meier curves compared survival of patients that walked more or less than 350 m by age categories.

The 6MWD is decreased in women with COPD. Values decrease with age and GOLD stages. Age, BMI, smoking status, comorbidities, MRC and FEV(1%) are statistical significant predictors of 6MWD. A 350 m cut-off value has a good sensitivity and specificity to predict (73% and 80% respectively) and differentiate survival (p < 0.001 for log rank comparisons) in these patients.

In women with COPD, the 6MWD decreases with age and GOLD stages. A 350 m distance is a valid threshold to differentiate survival. Further studies in different settings should confirm our findings.