Depression has long been associated with Alzheimer's disease and was recently found to have a causal relationship. Researchers used data from the largest and most recent genome-wide association studies (GWAS). These included a 2019 analysis of depression among 807,553 individuals and a 2019 study of Alzheimer's disease among 455,258 individuals. The researchers also accessed postmortem brain samples, which allowed use of deep-brain proteomic data to help determine molecular links between depression and Alzheimer's disease.
The investigators also applied Mendelian randomization to determine causality between depression and Alzheimer's disease. After assessing the effect of 115 independent single-nucleotide polymorphisms (SNPs) from the GWAS of depression, researchers uncovered significant evidence "that the SNPs cause depression, which in turn cause Alzheimer's disease." The researchers conducted the same analysis on 61 significant SNPs from the GWAS of Alzheimer's disease but did not find evidence to conclude that Alzheimer's disease causes depression.
Caffeine has not been found to have a causal relationship with Alzheimer's disease. In fact, some studies have demonstrated a lower incidence of Alzheimer's disease in patients who consume caffeinated coffee; however, no conclusive evidence supports its use in prevention.
Lifelong low body mass index was not found to be a causal risk factor for Alzheimer's disease. However, weight loss during midlife has been associated with increased dementia-related mortality risk more than three decades later. Weight gain was associated with reduced risk.
A recent study determined that Lyme disease is not associated with the development of either Alzheimer's disease or Lewy body dementia. Researchers found that Borrelia burgdorferi infection is not likely responsible for either condition.
Learn more about the etiology for Alzheimer's disease.
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Cite this: Helmi L. Lutsep. Fast Five Quiz: Alzheimer's Disease - Medscape - May 06, 2022.