Diaphragm paralysis after nephrectomy

Abstract decided to apply categorisation of some continuous variables in our study. On the other hand, we should mention that this transformation of variables did not modify the results, as both age and the number of exacerbations behaved as independent prognostic factors on inclusion in the model as continuous variables. Specifically, in this predictive equation, age proved to be an independent prognostic variable with an OR of 1.06 (95% CI 1.01 to 1.11). The same applies to the number of exacerbations with an OR of 1.20 (95% CI 1.03 to 1.39). Secondly, with regard to the role of age as a predictor of mortality, different studies involving both stable patients2 and acute cases3 4 have also found age to be an adverse prognostic factor. Despite such evidence, we consider the hypothesis suggested by Yohannes—that other age related and potentially modifiable variables would determine the prognostic effect attributed to age—to be very interesting. Unfortunately, in our analysis we did not include measures such as social support, physical disability, depression, or quality of life so we are unable to assess their specific weight. Almagro et al,5 in a study that also explored mortality predictors after hospitalisation and which considered variables of this kind, found age to have a predictive value in the univariate analysis, but this effect disappeared in the multivariate study. Therefore, as suggested by Yohannes, it is probable that the effect of age may be minimised when other predictors that condition or define such an effect are included in the model. In conclusion, age dichotomisation did not substantially change the results and conclusions drawn in our study. Re-analysis of the data using continuous (non-dichotomised) variables continues to suggest that severe exacerbations are independent predictors of mortality.