Cognitive functioning of individuals aged 90 years and older without dementia: A systematic review

Introduction Reference values to define cognitive impairment in individuals aged 90 years and older are lacking. We systematically reviewed the literature to determine the level of cognitive functioning of individuals aged 90 years and older without dementia. Methods The search identified 3972 articles of which 20 articles were included in the review. We calculated mean cognitive test scores and cut-off scores for cognitive tests published in two or more articles. Results The mean cognitive test scores (SD)/cut-off scores for individuals aged 90 years and older without dementia of the five most commonly used cognitive tests were: MMSE: 26.6 (2.6)/23.3 points, Digit Span forward: 5.9 (1.8)/3.6 digits, Digit Span backward: 4.4 (1.6)/2.4 digits, TMT-A: 85.8 (42.5)/140.2 s and TMT-B: 220.3 (99.2)/347.3 s. Discussion We provided mean cognitive test scores and cut-off scores that will improve the diagnostic process of cognitive impairment in individuals aged 90 years and older.