We thank Dr. Sidiropoulos for the valuable comment on our article1and agree that predictors are important for counseling patients. Reassuringly, the improvement of the quality of life (QoL) compared with only medical treatment for patients at an earlier stage, and for those at advanced stages, are very similar (24% and 27%, respectively),2,3but the causes for this may differ. Although the only factor predicting the improvement of the QoL at follow-up was a poorer QoL at baseline,1in the EARLYSTIM population, we found the duration of “off” time to be the most important predictor for improvement of the QoL in the advanced population.4Not only the duration but also the differences of disease severity—both in the medication “on” and “off” states—after surgery may account for this. We found a number of factors in the advanced patients for which the change scores showed a correlation with QoL improvement (anxiety, depression, motor severity, and “off” time),4but they cannot be regarded as predictors because the change is only known after surgery. The purpose of the recent publication was to look for such predictors and we found the baseline QoL summary index to be a predictor. This has changed our patient counseling: we recommend deep brain stimulation of the subthalamic nucleus for patients with early Parkinson disease if they have a disturbance in their QoL which is judged clinically relevant.