Likewise the hypothesis is, that as infants go through states of cognitive development, people with Alzheimers disease go through the reverse process of progressive cognitive impairment.The association with celiac disease is unclear, with a 2019 study finding no increase in dementia overall in those with CD, while a 2018 review found an association with several types of dementia including Alzheimers disease. Pathophysiology
Neuropathology
Alzheimers disease is characterised by loss of neurons and synapses in the cerebral cortex and certain subcortical regions. This loss results in gross atrophy of the affected regions, including degeneration in the temporal lobe and parietal lobe, and parts of the frontal cortex and cingulate gyrus. Degeneration is also present in brainstem nuclei particularly the locus coeruleus in the pons. Studies using MRI and PET have documented reductions in the size of specific brain regions in people with Alzheimers disease as they progressed from mild cognitive impairment to Alzheimers disease, and in comparison with similar images from healthy older adults.Both Aβ plaques and neurofibrillary tangles are clearly visible by microscopy in brains of those with Alzheimers disease, especially in the hippocampus. However, Alzheimers disease may occur without neurofibrillary tangles in the neocortex. Plaques are dense, mostly insoluble deposits of beta-amyloid peptide and cellular material outside and around neurons. Tangles (neurofibrillary tangles) are aggregates of the microtubule-associated protein tau which has become hyperphosphorylated and accumulate inside the cells themselves.
Memory and cognitive functions can be improved with aerobic exercises including brisk walking three times weekly for forty minutes. It may also induce neuroplasticity of the brain. Participating in mental exercises, such as reading, crossword puzzles, and chess have shown a potential to be preventative. Meeting the WHO recommendations for physical activity is associated with a lower risk of AD.Higher education and occupational attainment, and participation in leisure activities, contribute to a reduced risk of developing Alzheimers, or of delaying the onset of symptoms. This is compatible with the cognitive reserve theory, which states that some life experiences result in more efficient neural functioning providing the individual a cognitive reserve that delays the onset of dementia manifestations. Education delays the onset of Alzheimers disease syndrome without changing the duration of the disease.Cessation in smoking may reduce risk of developing Alzheimers disease, specifically in those who carry APOE ɛ4 allele. The increased oxidative stress caused by smoking results in downstream inflammatory or neurodegenerative processes that may increase risk of developing AD. Avoidance of smoking, counseling and pharmacotherapies to quit smoking are used, and avoidance of environmental tobacco smoke is recommended.Alzheimers disease is associated with sleep disorders but the precise relationship is unclear. It was once thought that as people get older, the risk of developing sleep disorders and AD independently increase, but research is examining whether sleep disorders may increase the prevalence of AD. One theory is that the mechanisms to increase clearance of toxic substances, including Aβ, are active during sleep.