Can low-income people afford life satisfaction? The modifying effect of personality traits, a cross-sectional study

The aim was to investigate whether the "Big Five" personality traits modify the association between household income and life satisfaction (LF); and to evaluate the interaction and main effects of personality traits and income on LF. Data from the Dental Care and Oral Health Study (DCOHS, 2015-2016) was used for the cross-sectional study (n = 3,475). Multivariable Poisson regression models (adjusted for demographics and health behaviours) assessed the effect of personality traits (measured using the Ten-Item Personality Inventory) on the association between income and LF (measured by the Satisfaction With Life Scale) using prevalence ratios (PRs). The Relative Excess Risk due to Interaction (RERI) was calculated to assess the direction of effect modification. Among low-income respondents, low LF was less prevalent in those with high personality trait scores than those with low scores. The difference in the prevalence of low LF by personality traits was greater between low versus high income for openness (11.4% vs 7.7%), agreeableness (12.3% vs 9.4%) and emotional stability (26.1% vs 20.2%) categories. The combined effects of low income and low scores for these traits on LF also exceeded the sum of their individual effects, as shown by their positive RERIs. The association between low income and low LF was modified by high openness, agreeableness and emotional stability scores. Findings suggest that psychological interventions for improving LF would be most beneficial in low-income groups.