APOE alleles are associated with sex-specific structural differences in brain regions affected in Alzheimer's disease and related dementia

Beneficial Effect of Societal Factors on APOE-ε2 and ε4 Carriers' Brain Health: A Systematic Review

BACKGROUND

Apolipoprotein-E (APOE) ε4 and ε2 are the most prevalent risk-increasing and risk-reducing genetic predictors of Alzheimer's disease, respectively. However, the extent to which societal factors can reduce the harmful impact of APOE-ε4 and enhance the beneficial impact of APOE-ε2 on brain health has not yet been examined systematically.

METHODS

To fill this gap, we conducted a systematic review searching for studies in MEDLINE, Embase, PsycINFO, and Scopus until June 2023, that included: (a) 1 of 5 social determinants of health (SDH) identified by Healthy People 2030, (b) APOE-ε2 or APOE-ε4 allele carriers, (c) cognitive or brain-biomarker outcomes, and (d) studies with an analysis of how APOE-ε2 and/ or APOE-ε4 carriers differ on outcomes when exposed to SDH.

RESULTS

From 14 076 articles retrieved, 124 met the inclusion criteria. In most of the studies, exposure to favorable SDH reduced APOE-ε4's detrimental effect and enhanced APOE-ε2's beneficial effect on cognitive and brain-biomarker outcomes (cognition: 70.5%, n: 74/105; brain-biomarkers: 71.4%, n: 20/28). A similar pattern of results emerged in each of the 5 Healthy People 2030 SDH categories, where finishing high school, having resources to satisfy basic needs, less air pollution, less negative external stimuli that can generate stress (eg, negative age stereotypes), and exposure to multiple favorable SDH were associated with better cognitive and brain health among APOE-ε4 and APOE-ε2 carriers.

CONCLUSIONS

Societal factors can reduce the harmful impact of APOE-ε4 and enhance the beneficial impact of APOE-ε2 on cognitive outcomes. This suggests that plans to reduce dementia should include community-level policies promoting favorable SDH.

Alzheimer's-related brain damage shows sex-specific links with risk factors

Alzheimer's disease is marked by brain damage from tau and amyloid aggregates, particularly to the hippocampus and the default network. A new study in PLOS Biology shows sex differences in the patterns of damage and in their association with risk and protective factors.