Intact circadian rhythm despite cortisol hypersecretion in Alzheimer's disease: A meta-analysis
Ursula G Saelzler1, Paul Verhaeghen2, Matthew S Panizzon1
1Department of Psychiatry, University of California San Diego, 9500 Gilman Dr. La Jolla, San Diego, CA 92093, USA.
Psychoneuroendocrinology
|August 2, 2021
Summary
Individuals with Alzheimer's disease (AD) exhibit elevated basal cortisol levels, but their cortisol circadian rhythm remains intact. This meta-analysis confirms cortisol hypersecretion in AD, suggesting hippocampal deterioration impacts the HPA axis.
Area of Science:
- Neuroendocrinology
- Geriatric Medicine
- Molecular Psychiatry
Background:
- Hypersecretion of cortisol, a glucocorticoid hormone, is a long-suspected phenomenon in Alzheimer's disease (AD).
- Decades of research have explored the link between AD and cortisol levels, necessitating a comprehensive review.
Purpose of the Study:
- To systematically review and meta-analyze existing literature on cortisol levels in individuals with AD.
- To determine if participant and methodological factors influence cortisol hypersecretion in AD.
- To assess the integrity of the cortisol circadian rhythm in individuals with AD.
Main Methods:
- A meta-analysis and systematic review of over 300 comparisons of hypothalamic-pituitary-adrenal (HPA) axis functioning.
- Comparison of basal cortisol indices between individuals with AD and cognitively normal older adults.
- Analysis of participant characteristics and time-of-day sampling for effect modification.
Main Results:
- A significant association between AD and basal cortisol elevations (g = 0.45) was found.
- No systematic impact of participant characteristics or sampling time on cortisol hypersecretion magnitude was observed.
- No evidence of group differences in direct indices of cortisol circadian rhythmicity, including the cortisol awakening response and diurnal slope.
Conclusions:
- Basal hypersecretion of cortisol, not circadian dysrhythmia, characterizes individuals with Alzheimer's disease.
- Observed hypersecretion aligns with theories of AD-induced hippocampal deterioration and reduced HPA axis inhibition.
- Further research is needed to clarify the role and timing of cortisol elevations in AD progression.
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