Socioeconomic status, life-course reserve-related indicator strata, reserve-related behavioural engagement patterns and incident dementia risk: a prospective UK Biobank study

Background This study investigated whether socioeconomic status (SES), life-course reserve-related indicator strata and behavioural engagement patterns were independently and jointly associated with incident all-cause dementia. Methods We included 500 846 dementia-free UK Biobank participants recruited in 2006–2010 and followed to September 2024. SES was defined using household income and Townsend Deprivation Index. Educational attainment and occupational complexity were cross-classified into four life-course reserve-related indicator strata. Behavioural engagement patterns were derived by latent class analysis of television viewing, confiding, social connection and leisure-activity diversity. Cox models adjusted for age, sex, ethnicity and APOE ε4 carrier status. Multiplicative interaction was assessed using product terms. Results During a mean 14.9-year follow-up (SD 2.5), 9813 participants developed dementia. Higher SES was associated with lower dementia risk (HR per unit higher SES score, 0.71; 95% CI 0.69 to 0.74). Compared with lower education and lower occupational complexity, higher education with lower complexity occupation (HR 0.91; 95% CI 0.84 to 0.98) and higher education with higher complexity occupation (HR 0.87; 95% CI 0.81 to 0.93) were associated with lower risk. The relatively higher-engagement behavioural pattern was associated with lower dementia risk than the lower-engagement pattern (HR 0.83; 95% CI 0.80 to 0.87). The association of behavioural engagement patterns with dementia did not differ across SES or life-course reserve-related strata. Conclusion SES, life-course reserve-related indicators and behavioural engagement represent related but distinct dimensions of dementia risk. Behavioural engagement may be relevant across socioeconomic and life-course contexts, while structural conditions shape participation opportunities.