After the age of 45, many aspects of one’s memory function begins to decline, including the overall processing speed of the brain. In the past, certain terms have been used to describe this cognitive decline associated with aging, namely, “age-associated cognitive decline,” “age-associated memory impairment” and “benign senescent forgetfulness.”
But, nowadays, the term “mild cognitive impairment” is used, as it is considered an intermediate stage between normal age-related memory decline and dementia such as Alzheimer’s disease.
However, certain memory functions do not show an age-related decline. One is procedural memory, such as acquiring and performing certain cognitive or motor skills. The other is semantic memory, such as facts and figures as they relate to general knowledge about the world.
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In the U.S.some form of dementia strikes about 27% of peopled aged 75 to 84 and 40% of those over 85. In 2007, there was an estimated 5.1 million Alzheimer’s disease cases in the U.S., of which just four percent were in people younger than 65. A further breakdown of late-onset Alzheimer’s disease shows that two percent of cases are people aged 65-74 years, 19% occur in people aged 75-84, and 42% of cases consist of people over 85.
Mild cognitive impairment is a stepping stone to more severe dementia such as Alzheimer’s disease. How quickly does this change occur? Within four years, mild cognitive impairment progresses to dementia in 65% of adults and to Alzheimer’s disease in 46%. In all, patients with mild cognitive impairment are seven times more likely to develop Alzheimer’s disease, compared to older people
without cognitive impairment.
Risk factors for Alzheimer’s disease include depression, health problems like diabetes or hypertension, genetics, concussions, smoking, and obesity. The four commonly prescribed drugs (donepezil,Â galantamine, rivastigmine and memantine) can only delayÂ the progression of several of the Alzheimer’s disease symptoms for six to 12 months. Moreover, 50% of thoseÂ treated with these drugs fail to respond. Therefore, in the last decade, the main research effort is to find effectiveÂ preventive interventions in healthy individuals, especiallyÂ the older individuals with their cognitive abilities intact, asÂ well as those diagnosed with mild cognitive impairment.