mean score of delirium severity rating scale during follow up period. Detailed information about scale: Korean Version of the Delirium Rating Scale-Revised-98(K-DRS-R98) DRS-R98 proved to be a valid and reliable instrument for the assessment of delirium severity and distinguish patients with delirium from non-delirious patients including dementia. The scale is composed of two sections. The first section is the severity scale, which consists of 13 items that are scored from 0 to 3 according to a Likert scale that is anchored by descriptions of phe-nomenology. The second section consists of three diagnostic items that are scored from 0 to 2 or 3. These items include temporal onset of symptoms, fluctuation of symptom severity and physical disorder. The total scale is comprised of 16 items. The total score is the sum of the scores for each item and the higher the score, the greater the severity.