Table 1 Definitions of cognitive and functional status used in the OPRAA cohort

Cognitive status classification

 •Known dementia: diagnosis of dementia recorded in SMR01 or SMR04, or prescription for cognitive enhancing medications (anticholinesterase inhibitor or memantine) in community prescribing data, or self or informant report of diagnosed dementia in OPRAA

 •Delirium: presence of full syndromic delirium based on positive score using the Confusion Assessment Method [39], or a clinical diagnosis of delirium made by specialist nurse assessment

 •Delirium superimposed on known dementia: combination of first two categories

 •Unspecified cognitive impairment: abbreviated mental test score [40] of <8/10 in the absence of a diagnosis of dementia or delirium

Functional status classification

 Activities of daily living (ADL) status was assessed using the Katz Index which assesses independence in six domains, with a maximum of six points for independence in all domains [41]. Evaluation was made about the Katz Index on admission and 3 months prior to admission, based on patient or informant response. Three categories were created:

  •Persistently high ADL score ≥ 5 both prior to and on admission

  •Acutely changed ADL score ≥ 5 3 months before admission with score < 5 on admission

  •Persistently low ADL score < 5 both prior to and on admission