Efficacy and Safety of Suvorexant (MK-4305) for Reducing Incidence of Delirium in Japanese Participants at High Risk of Delirium (MK-4305-085)

Inclusion Criteria: * Is hospitalized for (1) acute disease with severe disease state or decreased daily living function or (2) elective surgery requiring general anesthesia scheduled on the day after or 2 days after admission/Day 1 * Has (1) mild cognitive impairment or mild dementia and/or (2) a history of delirium in any prior hospitalization * Requires hospitalization for 6 days for acute disease, with treatment starting on day of admission; or 7 days, with treatment starting the day after admission OR * Requires hospitalization for 6 days for elective surgery scheduled on the day after admission; or for 7 days for elective surgery scheduled 2 days after admission * Is able to take study medications orally Exclusion Criteria: * Has moderate or severe dementia * Has a history of epilepsy or Parkinson's disease * Currently uses psychotropic agents or has a mental condition including schizophrenia, other mental disorders, bipolar disorder and major depression * Has a history of drug or alcohol abuse in the 5 years prior to start of study or has alcoholic disease such as alcoholic liver disease or gastritis alcoholic * Has a history of narcolepsy or cataplexy * Has used hypnotics, antipsychotics, mood stabilizers, antidepressants, anxiolytics, psychostimulants, anticonvulsants or tiapride within 2 weeks prior to randomization * Has delirium as assessed by DSM-5 or DRS-R-98 (total score ≥14.5) before the first dose of study medication