Clinical Outcomes and Factors Associated with Neuroleptic Malignant Syndrome in Older Patients: A Case Control Study

Background/Objectives: Older adults are vulnerable to multiple neuropsychiatric diseases. Antipsychotics and dopamine agents are widely used and are associated with neuroleptic malignant syndrome (NMS). However, NMS has still received limited focus in older Thai adults. This study aimed to evaluate the factors associated with NMS in older Thai adults and to review the clinical manifestations, adverse outcomes, severity, preventability, and management of NMS. Methods: The case–control study was conducted on older patients aged ≥ 60 years admitted to Ramathibodi Hospital between 1 August 2008, and 31 July 2022. Data were retrieved from electronic medical record reviews. Patients with NMS were identified by the documented International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) code G21.0 or ICD-9 code 333.92. The non-NMS or control group was matched by age, sex, time of admission, and agent exposure 14 days before the index date. Results: Fifty-four older patients admitted to the hospital were enrolled in this study. Of all, nine (16.7%) were diagnosed to have NMS. The most common causes of NMS were antipsychotic exposure (6 cases). All NMS events were considered to be “preventable” (scores of 4–6) according to the Likert scale. The independent factor associated with NMS was antipsychotic dose > 1 defined daily doses (DDDs) (OR 11.31, 95% CI 1.05–121.84, p = 0.045). Conclusions: NMS is a preventable condition. Most NMS cases develop from antipsychotic exposure. In addition, a higher daily dose of antipsychotics is associated with the development of NMS.