Heterogeneous effect of social and behavioral determinants of health on the risk of dementia

Abstract Background Individuals experiencing socioeconomic disadvantages are disproportionally affected by dementia. Social and behavioral determinants of health (SBDH) are major contributors to health inequities in dementia risk and outcomes. We aimed to determine the heterogeneous effect of SBDH on dementia risk in older adults. Method Using data from the National Alzheimer’s Coordinating Center (NACC) (2005‐2021), we identified adults 65 years and older with ≥2 visits and normal cognition at baseline. Exposures of interest included four SBDH collected at baseline, including alcohol abuse, drug abuse, smoking, and high school education or above. We applied a causal machine learning model and doubly robust learning to estimate the conditional average treatment effects (CATEs) and heterogenous effect of SBDH on the risk of dementia. Following the doubly robust learning framework, we created the models in a two‐step process: a first model that estimates the probability of being exposed (i.e., generating propensity scores), and then a second model that estimates dementia outcome from the exposures of interest, accounting for the probability of being exposed. Hyperparameter optimization and model validation were conducted based on minimal mean square error. Results We included 10,375 participants, with a mean age of 75 (SD: 7) years; 64% were women and 9% (n = 954) developed dementia over a median follow‐up of 5.2 years. In the estimation of CATEs, higher education was associated with a lower risk of dementia (absolute risk deference: ‐0.038; 95%CI, ‐0.065 to ‐0.01), while smoking (‐0.002; ‐0.009 to 0.005), alcohol abuse (‐0.073; ‐0.152 to 0.005), and drug abuse (‐0.024; ‐0.051 to 0.004) were not significantly associated with dementia risk. However, we identified a heterogeneous effect for each of these SBDH ( Figure ). Over 53%, 68%, and 28% of individuals had an increased risk of dementia with exposure to smoking, alcohol abuse, and drug abuse, respectively. Conclusion We identified significant heterogeneous effects of SBDH, specifically smoking, alcohol abuse, and drug use, on dementia risk in a group of older adults with normal cognition. Our findings underscore the need to adopt an individualized approach to address dementia disparities. Future studies should examine the mechanisms underlying the heterogenous effects of SBDH on dementia risk.