1 KITE-Toronto Rehabilitation Institute, University Health Network, Toronto, Canada.
2 Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada.
3 Division of Geriatric Medicine, Department of Medicine, Dalhousie University, Halifax, Canada.
4 Department of Health Studies, University College, University of Toronto, Toronto, Canada.
5 Department of Surgery, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
6 Canadian Centre for Health and Safety in Agriculture, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
7 Department of Psychology, University of Saskatchewan, Saskatoon, Canada.
8 Department of Psychology, Centre for Research in Human Development, Concordia University, Montreal, Canada.
9 Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Canada.
10 School of Optometry, Université de Montréal, Montreal, Canada.
11 Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Toronto, Canada.

Objectives: This study tested the association between neuroticism and six cognitive measures, and examined the potential mediating roles of social connection (social isolation and loneliness) among middle-aged and older adults.

Methods: This cross-sectional study was a secondary analysis of the Canadian Longitudinal Study on Aging (CLSA) Comprehensive Cohort, a sample of Canadians aged 45-85 years at baseline. Respondents with data collected at the first follow-up, between 2015 and 2018, were included (n = 27,765). Structural equation modelling was used to assess the association between neuroticism and six cognitive measures (Rey Auditory Verbal Learning Test immediate recall and delayed recall, Animal Fluency Test, Mental Alternation Test, Controlled Oral Word Association Test and Stroop Test interference ratio), with direct and indirect effects (through social isolation and loneliness). All analyses were stratified by sex, including females (n = 14,133) and males (n = 13,632).

Results: In unadjusted models, there was evidence of associations between neuroticism and all cognitive measures, except the Stroop Test interference ratio, suggesting higher neuroticism was associated with lower scores on memory and executive function tests. In the models of these other five outcomes, there was consistent evidence of indirect effects (through social isolation and loneliness) and, in some cases, direct effects. The results are discussed in context with limitations, including the use of cross-sectional design and alternative hypotheses to explain the association between personality and cognition.

Conclusion: Among middle-aged and older adults, for both males and females, the findings suggest that the association between neuroticism and cognitive outcomes may be mediated by aspects of social connection.