The Association between Autistic Traits and Trajectories of Anxiety in Middle-Aged and Older Adults: An 8-year Growth Mixture Model Analysis

Abstract Anxiety is common in autistic people, yet little is known about its course beyond midlife due to limited longitudinal research. We analysed data from 5,270 adults aged 50–91 (median 62; 75% female) in the PROTECT study. Participants completed the Autistic Spectrum Traits questionnaire and GAD-7. Sixty-six (~1.3%, 72.3% female) had high autistic traits (AST group), while 3,874 (~73.5%, 77.8% female) reported none (Control Older Adults; COA). Growth mixture modelling (GMM) identified anxiety trajectories over eight years. Associations between AST status and trajectory membership were examined using multinomial logistic regression.GMM revealed three trajectories: persistently minimal symptoms (‘lower-range minimal’ 85.6%; ‘upper-range minimal’ 12.4%), and a third showing rising anxiety from mild to clinical levels (1.9%). Regressions showed AST individuals were more likely than COA to follow the mild-to-clinical trajectory (RR 4.41, 95% CI 1.70–11.44). Elevated autistic traits increase risk of worsening anxiety with age, highlighting the need for tailored support.