en Clinical Neuroscience Clinical Neuroscience Review Review <strong>Introduction</strong>: Patients in the early stages of Parkinson disease (PD) may have subtle cognitive deficits, while overt cognitive deficits are usually manifestations of late-stage PD. There is still a debate on the outcome of deep brain stimulation (DBS) on the cognitive function of PD patients. This study aimed to investigate the effect of subthalamic nucleus (STN)-DBS on the dementia of PD patients after surgery compared to medical therapy and other procedures.&nbsp;<br> <strong>Methods</strong>: We searched PubMed, Scopus, Cochrane Library, and Web of Science database on October 2020, with keywords: &ldquo;Deep brain stimulation,&rdquo; &ldquo;Parkinson disease,&rdquo; &ldquo;dementia,&rdquo; and &ldquo;memory.&rdquo; Reviews, abstracts, case presentations, and letters were excluded.&nbsp;<br> <strong>Results</strong>: In total, 491 studies were screened after removing the duplicates. The screening results yielded 81 articles to be screened for eligibility. Finally, 6 studies were included in this meta-analysis for synthesis. Overall, 800 patients were included in this meta-analysis, using the Mattis dementia rating scale (MDRS) and descriptive data from the articles extracted to assess global dementia.<br> <strong>Conclusion</strong>: Our results suggest that the STN-DBS group showed a larger cognitive decline than the patients receiving the best medical treatment (BMT). However, comparing STN-DBS with globus pallidus interna stimulation and pallidotomy could not demonstrate a significant statistical effect on the global dementia of patients. More long-term studies with larger sample sizes are needed to validate current findings.&nbsp; Subthalamic nucleus, Parkinson disease, Deep brain stimulation, Parkinson disease dementia 157 164 http://bcn.iums.ac.ir/browse.php?a_code=A-10-3420-1&slc_lang=en&sid=1 Ali Razmkon ali.razmkon@gmail.com 13700319475328460049030 13700319475328460049030 No Research Center for Neuromodulation and Pain, Shiraz University of Medical Sciences, Shiraz, Iran. Saeed Abdollahifard Saeed_abdf@hotmail.com 13700319475328460049031 13700319475328460049031 Yes Research Center for Neuromodulation and Pain, Shiraz University of Medical Sciences, Shiraz, Iran. Hirad Rezaei 13700319475328460049032 13700319475328460049032 No Research Center for Neuromodulation and Pain, Shiraz University of Medical Sciences, Shiraz, Iran. Amir Reza Bahadori 13700319475328460049033 13700319475328460049033 No Research Center for Neuromodulation and Pain, Shiraz University of Medical Sciences, Shiraz, Iran. Parham Eskandarzadeh 13700319475328460049034 13700319475328460049034 No Research Center for Neuromodulation and Pain, Shiraz University of Medical Sciences, Shiraz, Iran. AmirAli Rastegar Kazerooni 13700319475328460049035 13700319475328460049035 No Research Center for Neuromodulation and Pain, Shiraz University of Medical Sciences, Shiraz, Iran.