Theories of Alzheimer’s disease: Amyloid hypothesis, blood-brain barrier hypothesis and cholinergic hypothesis

Abstract

Alzheimer’s disease (AD) is the biggest drain on society’s resources in the developed world. AD accounts for between 60 and 80 percent of dementia cases in older persons, making it the most prevalent cause of dementia. This paper analyzes three theories and experiments about AD, which are amyloid hypothesis, blood-brain barrier (BBB) hypothesis and cholinergic hypothesis. The amyloid hypothesis suggests that cognitive decline in patients is caused by the accumulation of amyloid beta (Aβ), which creates plaques that block the efficient transmission of neuronal signals. The BBB hypothesis suggests that the breakdown of the integrity of the BBB allows harmful substances and immune cells to enter the brain, causing inflammation and neuronal damage, which leads to cognitive decline in Alzheimer’s patients. The cholinergic hypothesis proposes that AD is caused by the nervous system’s reduced production of the neurotransmitter acetylcholine.