Life expectancy continues to rise in most countries around the world, and in industrialized nations it is not uncommon for people to live well into their 90s. One consequence is that dementia will become much more common, as a new study reported by Fiona Matthews ,Carol Brayne and the Medical Research Council Cognitive Function and Ageing Study Investigators published in the open-access international medical journal PLoS Medicine suggests.
A widespread myth is that once a person reaches 80 and is mentally healthy, they are likely to die without mental incapacitation. The new results clearly show that this is not the case. The researchers followed a representative population of aged people over several years to estimate the risk of developing cognitive impairment or dementia near the end of life, and to determine whether factors such as education and social class, which may appear protective earlier in life, can ultimately prevent decline in mental functioning.
Using standardized assessments of cognitive status, the researchers interviewed people age 65 and over at six sites representing rural and urban areas in the UK. Interviews were conducted at regular intervals over 10 years. Of approximately 12,000 study participants who had died by the time of this report, just over 2,500 had an assessment for dementia within one year before dying. Of this group, those who died between ages 65 and 69 had a 6% chance of dying with dementia, and those who died above age 95 had a 58% chance of dying with dementia. When moderate or severe cognitive impairment were included, the rate in people above age 95 reached almost 80%. Women were more likely to develop dementia than men, even after taking into account the fact that women tend to live longer than men. A higher level of education was associated with only a slightly lower risk of dementia before death.
As Willem van Gool (Academic Medical Center, Amsterdam) states in an accompanying Perspective, despite the sobering nature of these data, there is room for slightly more hopeful interpretations that take into account the age of onset or duration of dementia rather than the absolute numbers. While many elderly people indeed wonder how likely it is that they will "lose their mind" before they die, if preventative measures manage to delay the onset of dementia, they would still yield enormous benefits. To prove that preventative measures work, however, will not be an easy task, and societies with aging populations should be prepared for large numbers of elderly patients with dementia.
Citation: Brayne C, Gao L, Dewey M, Matthews FE, Medical Research Council Cognitive Function and Ageing Study Investigators (2006) Dementia before death in ageing societies--The promise of prevention and the reality. PLoS Med 3(9): e397 (http://dx.doi.org/10.1371/journal.pmed.0030397)
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