Insights for dementia risk reduction among lower SES adults in OECD countries: scoping review of interventions targeting multiple common health risk factors.

The number of people living with dementia is expected to rise to 153 million cases globally by 2050. This will come at a high economic and human cost to societies with disproportionate effects on socioeconomically disadvantaged groups who experience greater exposures to- and fewer protections from- the environmental, social and behavioural drivers of dementia risk. Almost half (45%) of dementia incidence could theoretically be prevented or delayed by addressing 14 modifiable risk factors. While several studies have demonstrated the feasibility of multidomain dementia risk reduction interventions in relatively older, educated and wealthy populations, we are not aware of any studies to date explicitly targeting younger adults (< 50 years) with lower socioeconomic status. To inform future strategies, we conducted a scoping review of intervention studies targeting multiple 'dementia-related' risk factors among adults with lower socioeconomic status in developed country contexts. We identified 1003 unique records; 34 met our criteria for inclusion - involving more than 17,500 participants from 13 countries. While none of the studies explicitly targeted dementia risk reduction, they reported on 30 relevant multidomain interventions targeting common risk factors associated with dementia including; diet (28), physical inactivity (27), obesity (22), diabetes (9), hypertension (8), smoking (6), alcohol use (6), depression (3) and social isolation (1). While most studies recorded positive effects on one or more health behaviours, there was a diversity in the design, approach and outcomes of interventions, with significant intervention effects being associated with the use of a wider range of behaviour change techniques. We suggest that designing interventions to reduce dementia risk and disparities requires a high degree of contextual specificity and propose a structured and participatory approach.