Functional Reserve: Experience Participating in Instrumental Activities of Daily Living is Associated with Gender and Functional Independence in Mild Cognitive Impairment

Article type: Research Article

Authors: Berezuk, Courtney^a | Zakzanis, Konstantine K.^{a; b; *} | Ramirez, Joel^{c; d; e} | Ruocco, Anthony C.^{a; b} | Edwards, Jodi D.^{c; d; e} | Callahan, Brandy L.^{c; d} | Black, Sandra E.^{c; d; e; f} | for the Alzheimer’s Disease Neuroimaging Initiative¹

Affiliations: [a] Graduate Department of Psychological Clinical Science, University of Toronto, Toronto, ON, Canada | [b] Department of Psychology, University of Toronto Scarborough, Toronto, ON, Canada | [c] LC Campbell Cognitive Neurology Research Unit, Sunnybrook Heath Sciences Centre, Toronto, ON, Canada | [d] Hurvitz Brain Sciences Program, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada | [e] Canadian Partnership for Stroke Recovery, Sunnybrook Health Sciences Centre, Toronto, ON, Canada | [f] Institute of Medical Science, Faculty of Medicine (Neurology), University of Toronto, Toronto, ON, Canada

Correspondence: [*] Correspondence to: Konstantine K. Zakzanis, PhD, CPsych, University of Toronto Scarborough, SY143, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada. Tel.: +416 287 7424; E-mail: zakzanis@utsc.utoronto.ca.

Note: [1] Data used in preparation of this article were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database (http://adni.loni.usc.edu) on June 24, 2016. As such, the investigators within the ADNI contributed to the design and implementation of ADNI and/or provided data but did not participate in analysis or writing of this report. A complete listing of ADNI investigators can be found at: http://adni.loni.usc.edu/wp-content/uploads/how_to_apply/ADNI_Acknowledgement_List.pdf

Abstract: Background: Gender differences in instrumental activities of daily living (IADLs) in mild cognitive impairment (MCI) and Alzheimer’s disease may be explained by gender differences in IADL involvement. Objective: We introduce a novel theoretical construct, termed functional reserve, and empirically examine gender differences in IADL experience as a proxy of this reserve. Methods: We cross-sectionally examined men (n = 502) and women (n = 340) with MCI from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Demographic factors, depressive symptoms, neuropsychological scores, and IADL experience were included as independent variables and total Functional Activities Questionnaire (FAQ) scores as the dependent variable. Regression analyses were performed on the full cohort and stratified by gender to identify differential predictive relationships for men and women. Results: Gender was associated with total FAQ (p < 0.05) until adjusting for IADL experience. Furthermore, the combination of cognitive measures accounted for the most variance in functional dependence (12% explained, p < 0.001), although IADL experience was the most important single variable (4.8% explained, p < 0.001). Stratification by gender revealed that IADL experience accounted for 6.6% of the variance in FAQ score in men (p < 0.001) but only 2.4% in women (p = 0.001); however, the interaction between gender and experience was not statistically significant. Discussion: A small effect of men showing greater functional dependence in MCI may be explained by lower IADL experience. Additionally, IADL experience was associated with superior functioning in all analyses, potentially through increased functional reserve. This concept of functional reserve may have implications for identifying individuals at risk for IADL dependence, preventing or delaying decline, and potentially treating functional impairment.

Keywords: Activities of daily living, cognitive reserve, disability, functional impairment, instrumental activities of daily living, sex differences

DOI: 10.3233/JAD-161227

Journal: Journal of Alzheimer's Disease, vol. 58, no. 2, pp. 425-434, 2017