Inclusion and exclusion criteria with rationale
| Inclusion criteria | Rationale |
| ≥70 years of age | POD most commonly appears in older patients |
| Scheduled to undergo major orthopaedic surgery (total hip replacement, total knee replacement, spine surgery) | Major orthopaedic surgeries are associated with an increased risk for POD27 47 |
| Exclusion criteria | Rationale |
| Inability to give consent due to, but not limited to, pre-existing severe dementia (diagnosis or MMSE<18), Parkinson’s disease or other movement disorders, severe neurocognitive damage, severe psychiatric illness, blindness or deafness. | Inability to ethically enrol individuals of this population due to study burden |
| Expected postoperative recovery for less than 24 hours | We will be unable to assess for POD |
| Patient with more than 2 days spent in the ICU during the month prior to surgery | Pre-existing operations/illnesses may temporarily disrupt sleep and confound the study |
| Patient with inability to wear actiwatch (due to, but not limited to, infection at the site of watch, allergies to the material of watch, limited mobility) | Required for activity rhythm assessment |
| Non-English-speaking or insufficient vision and/or hearing | Inability to administer cognitive assessments that are primarily validated in English |
ICU, intensive care unit; MMSE, Mini-Mental State Examination; POD, postoperative delirium.