Neurofibrillary tangles are composed of paired helical filaments (PHF). In normal, non-demented aging, the number of tangles in each affected cell body is relatively low and restricted to the olfactory nucleus, parahippocampal gyrus, amygdala and entorhinal cortex. As the non-demented individual ages, there is a general increase in the density of tangles, but no significant difference in where tangles are found. The other main neurodegenerative contributor commonly found in the brain of patients with AD is amyloid plaques. However, unlike tangles, plaques have not been found to be a consistent feature of normal aging. Role of oxidative stress
Cognitive impairment has been attributed to oxidative stress, inflammatory reactions and changes in the cerebral microvasculature. The exact impact of each of these mechanisms in affecting cognitive aging is unknown. Oxidative stress is the most controllable risk factor and is the best understood. The online Merriam-Webster Medical Dictionary defines oxidative stress as,  "physiological stress on the body that is caused by the cumulative damage done by free radicals inadequately neutralized by antioxidants and that is to be associated with aging." Hence oxidative stress is the damage done to the cells by free radicals that have been released from the oxidation process. Compared to other tissues in the body, the brain is deemed unusually sensitive to oxidative damage. Increased oxidative damage has been associated with neurodegenerative diseases, mild cognitive impairment and individual differences in cognition in healthy elderly people. In normal aging, the brain is undergoing oxidative stress in a multitude of ways.
Reviews of current literature studying natives in Australia, Brazil, Canada, and the United States from participants aged 45 to 94 years old reveal varied prevalence rates for cognitive impairment not related to dementia, from 4.4% to 17.7%. These results can be interpreted in the context of culturally biased neurocognitive tests, preexisting health conditions, poor access to healthcare, lower educational attainment, and/or old age. Sex
Women
Compared to their male counterparts, womens scores on the Mini Mental State Exam (MMSE) tend to decline at slightly faster rates with age. Males with mild cognitive impairment tend to show more microstructural damage than females with MCI, but seem to have a greater cognitive reserve due to larger absolute brain size and neuronal density. As a result, women tend to manifest symptoms of cognitive decline at lower thresholds than men do. This effect seems to be moderated by educational attainment - higher education is associated with later diagnosis of mild cognitive impairment as neuropathological load increases. Transgender Individuals
LGBT elders face numerous disparities as they approach end-of-life. The transgender community fears the risk of hate crime, elder abuse, homelessness, loss of identity, and loss of independence as they age. As a result, depression and suicidality are particularly high within the demographic. Intersectionality - the overlap of several minority identities - can play a major role in health outcomes, as transgender people can be discriminated against for their race, sexuality, gender identity, and age.