This pilot study will study the impact of critical illness and ICU processes of care on the trajectory and development of frailty. It is hypothesize that frailty in survivors of critical illness will be measurable at hospital discharge, will correlate with processes of care while in ICU and will better discriminate long term outcomes when compared to severity of illness or the degree of frailty present on ICU admission.

This pilot study will be conducted in a tertiary medical surgical ICU at Kingston General Hospital- Kingston, Ontario. It will inform the feasibility, timelines and sample size for the multi-center study and will allow for the refinement of study procedures and data collection methods. This study will be published separately as a stand-alone pilot.

Single Center Observational pilot study to inform on the conduct of a multi-center observational study.

Inclusion Criteria:

1. Age > 55 years
2. Admission to ICU for over 24 hours
3. Receipt of at least one therapeutic life support intervention that can only be delivered in the ICU such as mechanical ventilation (both invasive and non-invasive), vasoactive medications (vasopressors or inotropes) or acute renal replacement therapy.

Exclusion Criteria:

1. Lack of consent for study inclusion or lack of consent to be contacted for long term follow-up.

2. Expected to survive for less than 72 hours after ICU admission.

3. Inability to obtain baseline blood work less than 48 hours after ICU admission (i.e. study enrollment must occur within 48 hours of ICU admission allowing for the blood work to be done in the time allowed).

4. No family or caregivers available to collect collateral history.

5. Not able to speak English with lack of available medical translators.

6. Admission to ICU with acute structural neurological disease:

   1. Massive stroke requiring ICU care
   2. Spinal cord injury with neurological deficit

Individuals who are admitted to an intensive care unit requiring therapeutic life support.