Regarding “ Uvulopalatopharyngoplasty reduces the incidence of depression caused by obstructive sleep apnea ”

We would like to comment on the article titled “Uvulopalatopharyngoplasty Reduces the Incidence of Depression Caused by Obstructive Sleep Apnea” by Cho et al. In their published study, the authors suggest that uvulopalatopharyngoplasty (UPPP), a surgical treatment for obstructive sleep apnea (OSA), reduces the risk of comorbid depression. They analyzed approximately 160 thousand OSA patients retrospectively to investigate this. However, there are some points to be explained by the authors regarding their article. Firstly, neither the severity of OSA nor the success rate of UPPP is described. Therefore, we do not know the answers to the following questions: 1) How many patients with OSA who underwent successful UPPP have reduced depression symptoms? and 2) how did the level of depression of patients who underwent unsuccessful UPPP change postoperatively, or did it remain same after surgery? In this regard, the methodology is somewhat mis-designed. Secondly, the authors stated UPPP has a clinical effect on depression independent of apnea-hypopnea index (AHI)based judgment. If the authors consider that the severity of OSA can be evaluated with different parameters (other than AHI, oxygen desaturation index, etc.), they should identify these parameters. What would be the clinical effect of UPPP on depression independent of objective polysomnography data? When a surgical treatment in OSA is effective, that is, confirmed by postoperative polysomnography, the depression symptoms should regress as well. By contrast, if the depression continues despite significant improvements in OSA severity after surgery, this would suggest that the depression level in OSA depends on other factors. Considering that UPPP is not a highly successful surgical technique in OSA worldwide, what would be the therapeutic effect of this relatively low-successful surgical treatment on depression—or is undergoing a surgery just a psychologically good experience for patients? Epworth Sleepiness Scale scores were not even mentioned in the study design; this might be a partial explanation for these concerns. Thirdly, we do not even know which patients in the study population received effective antidepressant drug treatment. The strength of this study is its large cohort; however, the method of this article could had been prepared more meticulously by the authors. We wish that our comments do not diminish the importance of this article and the valuable effort of the authors.