Exploring interrelationships between lifestyle and demographic factors associated with cognitive functioning in mid-to-older New Zealanders : a thesis presented in partial fulfilment of the requirement for the degree of Master of Science in Psychology at Massey University, Palmerston North, New Zealand

Abstract

As the population ages, concerns around age-related conditions such as dementia rise. Characterised by severe cognitive impairment and thus significant reductions in cognitive functioning, beginnings of dementia can present in midlife and cause considerable challenges such as reduced functionality. The aim of the present study was to better understand the factors affecting cognitive functioning to inform a preventative focus. The present cross-sectional study investigated relationships between socioeconomic status (represented by education, income, current occupational status, and a composite variable) and cognitive functioning (measured using the ‘Kiwi’ Addenbrooke’s Cognitive Examination-Revised). This was assessed alongside sex and lifestyle-based modifiable risk (measured using a short-form Lifestyle for Brain Health (LIBRA) index). Data was sourced from the 2010 New Zealand Longitudinal Study of Ageing (NZLSA) cohort and included a subset of participants who had undertaken the voluntary cognitive assessments (N = 869, aged 48-75, 46.7% male, 26.4% Māori). Preliminary analyses (Kruskal-Wallis and Mann-Whitney) indicated that lower education, lower income, non-employment, male sex, and higher LIBRA tertile (indicative of a less brain healthy lifestyle) were associated with lower cognitive functioning. However, hierarchical multiple regression modelling indicated that, once controlling for covariates, only higher educational attainment (B = 1.48, 95% CI = [1.16, 1.80], p < 0.001), female sex (B = 1.26, 95% CI = [0.62, 1.89], p < 0.001), and lower LIBRA scores (B = -0.53, 95% CI = [-0.84, -0.22], p < 0.001) (along with covariates of younger age and non-Māori ethnicity) remained independently related to higher cognitive functioning. While the main-effects model explained 19% of variance, interaction terms testing moderation between independent variables were insignificant and unable to improve model fit. Findings suggest independent variables of education, sex, and lifestyle-based modifiable risk (LIBRA scores) all predict cognitive functioning individually, but not interactively. Thus, suggesting parallel and independent pathways of influences. Strategies to increase brain health should therefore support targeted interventions that address each factor directly and independently for healthier cognitive functioning. Future studies incorporating longitudinal data that utilises the full 12 factor LIBRA scale may be able to reveal more nuanced interactions and identify those most vulnerable.