Extent of cognitive decline

News reports

October 2007

National study of dementia prevalence

A study using data from 856 men and women who participated in the nationally representative Aging, Demographics and Memory Study estimates one in seven or 13.9% of the American population aged 71 and older, have some form of dementia. About 70% of those, or 9.7% of the population, have Alzheimer’s, and 17.4% of them have vascular dementia. As expected, the prevalence of dementia increased dramatically with age, from 5% of those aged 71 to 79 to 37.4% of those age 90 and older. With increasing age, Alzheimer’s disease accounted for progressively more of the dementia cases, so that in the 90+ age group, it comprised 79.5% of dementia cases, compared to 46.7% among those in their 70s. There was no difference between genders when corrected for education and age. Previous national estimates of dementia prevalence have been extrapolated from regional samples, and were generally significantly lower.
The findings were published in the November issue of Neuroepidemiology.   Full reference
Full text available at: http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ArtikelNr=109998&Ausgabe=233821&ProduktNr=224263&filename=109998.pdf http://www.eurekalert.org/pub_releases/2007-10/uom-oi7103007.php

March 2005

Most older people with mild cognitive impairment have Alzheimer's or cerebral vascular disease

Another finding from the Religious Orders Study. It seems that mild cognitive impairment is often the earliest clinical manifestation of Alzheimer’s or vascular dementia. By studying the brains of study participants after death, researchers could ascertain that, of the 37 individuals with mild cognitive impairment, 23 met pathologic criteria for Alzheimer's disease, and 12 had cerebral infarcts (5 had both). Only 9 did not have either pathology. The researchers conclude that even mild loss of cognitive function in older people should not, therefore, be viewed as normal, but as an indication of a disease process.
The study was published in the March 8 issue of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2005-03/rpsl-mop022805.htm

November 2003

A large-scale epidemiological study in the Netherlands has found an incidence of frontotemporal dementia that equates to a population level of 1.1 per 100,000. The prevalence was highest among those ages 60 to 69, at 9.4 per 100,000. The prevalence among people ages 45 to 64 was estimated to be 6.7 per 100,000. Symptoms began after age 65 in 22% of patients. Whites accounted for 99% of all cases despite an ample nonwhite population. A family history of dementia was present in 43% of patients.
The study was reported in the September issue of Brain. Full reference

December 2001

In the first population-based study of cognitive impairment in the United States, nearly one in four older African Americans in Indianapolis were found to have measurable cognitive problems (short of dementia or Alzheimer's). The prevalence of cognitive impairment grew significantly with age, with rates increasing by about 10 percent for every 10 years of age after age 65. Of those aged 85 and older, 38% had some degree of cognitive impairment. Surveys in other countries (which cannot be directly compared due to differences in methodology, diagnostic criteria, etc) have reported results ranging from 10.7% in Italy to 26.6% in Finland.
http://www.eurekalert.org/pub_releases/2001-11/nioa-cih110701.htm
http://www.eurekalert.org/pub_releases/2001-11/aaon-mla110501.htm

June 2001

Researchers from Leiden University tested the mental functioning of 599 Dutch men and women aged 85 years. Good mental speed on word and number recognition tests was found in 33% of the women and 28% of the men. Forty one per cent of the women and 29% of the men had a good memory. This despite the fact that significantly more of the women had limited formal education compared to the men (not surprising given the time in which they grew up). The authors suggested that biological differences - such as the relative absence of cardiovascular disease in elderly women compared with men of the same age - could account for these sex differences in mental decline.
The study appeared in the Journal of Neurology, Neurosurgery and Psychiatry, 71, 29-32.
http://www.eurekalert.org/pub_releases/2001-06/BSJ-Ewhb-1706101.htm

March 2001

Severe memory problems in older adults have become more rare, probably because of better treatments for dementia, depression and strokes. Researchers from the University of Michigan interviewed more than 10,000 people ages 70 and older from 1993 to 1998. People tested in 1998 did significantly better on the memory tests than those tested earlier. In 1998 less than 4% of those 70 and older showed severe memory problems, and only 8% of those 85 and older. Surprisingly, the greatest improvement was seen among those in their 80s and those with less than a high school education. The decline in memory problems is believed to be associated with the improvement in physical fitness seen among the elderly. It is speculated that the increase in number of women on hormone replacement therapy may also play a part.
The study is reported in the March issue of the Journal of Gerontology: Social Sciences.

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