[5] There are many different syndromes and pathologies that cause cognitive impairment including dementia, mild neurocognitive disorder, and Alzheimer's disease.
[2] Some known causes of cognitive impairments that are more common in younger people are: chromosomal abnormalities or genetic syndromes, exposure to teratogens while in utero (e.g., prenatal exposure to drugs), undernourishment, poisonings, autism, and child abuse.
[2] Screening for cognitive impairment in those over the age of 65 without symptoms is of unclear benefit versus harm as of 2020.
[6] In a large population-based cohort study included 579,710 66-year-old adults who were followed for a total of 3,870,293 person-years (average 6.68 ± 1.33 years per person), subjective cognitive decline was significantly associated with an increased risk of subsequent dementia.
As the maximum cognitive ability that we are able to achieve decreases, it may not actually affect our daily lives, which only require the normal level.
Another possible explanation is the selective survival effect, as the study participants who had a childhood with hunger tend to be the healthiest of their era.
[5] The role of light therapy for treating people with cognitive impairment or dementia is not fully understood.