The association between allostatic load and brain: A systematic review.

Area of Science:

• Neuroscience
• Psychiatry
• Public Health

Background:

• Allostatic load (AL) signifies chronic stress-induced dysregulation impacting key brain regions like the hippocampus, amygdala, and prefrontal cortex (PFC).
• Elevated AL is linked to adverse health outcomes, including psychiatric disorders, cognitive decline, and chronic somatic conditions.
• Understanding the brain-related mechanisms of AL-induced damage remains limited.

Purpose of the Study:

• To systematically review studies examining the association between the Allostatic Load (AL) index and brain structure/function in adults.
• To synthesize current evidence on how chronic stress-related biological dysregulations affect the brain.

Main Methods:

• Systematic literature search of PubMed/MEDLINE, CINAHL, Academic Search Complete, and Web of Science until August 9th, 2021.
• Qualitative synthesis of 13 selected studies investigating the AL index and brain parameters.
• Analysis of between-study heterogeneity in AL index calculation and brain measures.

Main Results:

• A high AL index was consistently associated with alterations in brain structure and function across studies.
• Specific associations included hippocampal and white matter changes in older adults, cortical and hippocampal alterations in schizophrenia spectrum disorders, and white matter/cortical changes in overweight individuals.
• Neurostructural alterations, such as white matter tract changes, may be observed across various populations, while others, like cortical thinning, appear specific to certain groups.

Conclusions:

• Elevated allostatic load is associated with diverse neurostructural and neurofunctional changes.
• Some brain alterations linked to AL may be population-independent (e.g., white matter tracts).
• Further research with standardized AL index calculation is needed to identify vulnerable populations and refine understanding of AL's neurobiological impact.