Study to Assess the Long Term Safety and Tolerability of ACT-541468 (Daridorexant) in Adult and Elderly Subjects Suffering From Difficulties to Sleep

Inclusion Criteria: * Signed informed consent prior to any study-mandated procedure (Visit 1). * Having completed the DB study treatment and the run-out period of ID-078A301 (NCT03545191) or ID-078A302 (NCT03575104). * For woman of childbearing potential, the following is required: * Negative urine pregnancy test (EOT of ID-078A301 or ID-078A302 studies) * Agreement to use the contraception scheme as required by the protocol from Visit 1 up to at least 30 days after EODBT. Exclusion Criteria: * Unstable medical condition, significant medical disorder or acute illness, C-SSRS©, ECG, hematology or biochemistry test results in ID-078A301 and ID-078A302, which in the opinion of the investigator could affect the subject's safety or interfere with the study assessments (Visit 1). * For female subjects: lactating or planning to become pregnant during the duration of the study (Visit 1). * Positive urine drug test (for benzodiazepines, barbiturates, cannabinoids, opiates, amphetamines, or cocaine) or presence of alcohol in exhaled breath as detected by breathalyzer test (EOT of ID-078A301 or ID-078A302 studies if same day as Visit 1 or Visit 1 if within 7 days after EOT).