Dementia in Oldest-Old Twice as Likely to Affect Women
By Crystal Phend
IRVINE, Calif., 4 july 2008-- The likelihood of women developing dementia as they age into their 90s is significantly greater than it is for men, according to researchers here.
Among women, dementia prevalence nearly doubled every five years after age 90 whereas prevalence reached a plateau among men, reported Maria M. Corrada, Sc.D., of the University of California Irvine, and colleagues online in Neurology.
These findings from one of the largest epidemiological studies in the oldest-old group suggested that the pattern of dementia changes for men late in life. Yet for women the doubling rate was similar to that in previous studies that typically included patients only up through age 85.
Men in Dr. Corrada's study who reached age 90 were about half as likely to have dementia than women in the same age group, which may have been at least partially because of shorter survival both overall and after dementia diagnosis, the researchers said.
"As the oldest-old are the fastest growing segment of the United States population," they wrote, "accurate estimates of dementia prevalence are crucial for public health planning."
Their population-based 90+ Study followed men and women longitudinally with cognitive assessments starting at age 90. It included 911 participants from the larger Leisure World Cohort Study of a retirement community in Orange County, Calif., initiated in the early 1980s.
The participants were mostly women (77%) and Caucasian (99%). About half of the participants still lived at home (56%), while 16% had moved to a nursing home and 28% to other group quarters.
The age distribution was nearly identical between genders, with an average age of 94.4 among men (range 90 to 105) and 94.5 among women (range 90 to 106).
At entry to the 90+ study, 375 participants (41.2%) had dementia from any cause. The prevalence was significantly lower among men than women (27.6% versus 45.2%, odds ratio 1.97, P<0.001).
The difference between genders carried through most age groups with a dementia prevalence that rose from 27% at ages 90 to 91 to 71% at ages 98 to 99 among women, compared with a fairly stable prevalence among men that rose only slightly from 21% to 33% at age 100 and beyond.
Likewise, dementia risk doubled every five years for women (OR 2.05, P<0.001) but did not rise significantly for men over the same period (OR 1.19, P=0.58).
Even after adjustment for the method with which dementia was determined, age and sex remained linked to dementia prevalence with little change in the odds ratios (P<0.001), suggesting this factor was unlikely to explain the disparity, the researchers said.
The authors did cite the fact that only some of the participants had an in-person evaluation as a limitation of the study.
However, education appeared to account for some of the difference. Women with more than a high school education were 36% to 45% less likely to develop dementia in old age than less educated women. Education was not a significant factor among men.
Dr. Corrada and colleagues speculated that women could have sex-specific dementia risk factors that increase at the end of life to raise incidence compared with men.
"The few men who reach age 90 and beyond may be 'survivors' with fewer risk factors for developing dementia," they said, "suggesting that the incidence of dementia does not increase (or may even decrease) for men over 90."
Another possibility is shorter duration of dementia in men rather than a change in incidence, they said. In addition to shorter survival among men in the general population, several studies have shown shorter survival among elderly men with dementia than among their female peers.
The investigators cautioned that the generalizability of the findings could be limited as the cohort was predominantly white, well educated, and richer.
The study was supported by the National Institutes of Health and the Al and Trish Nichols Chair in Clinical Neuroscience. The researchers reported no conflicts of interest.
Primary source: NeurologySource reference:Corrada MM, et al "Prevalence of dementia after age 90: results from The 90+ Study" Neurology 2008; 71: 337-343.
By Crystal Phend
IRVINE, Calif., 4 july 2008-- The likelihood of women developing dementia as they age into their 90s is significantly greater than it is for men, according to researchers here.
Among women, dementia prevalence nearly doubled every five years after age 90 whereas prevalence reached a plateau among men, reported Maria M. Corrada, Sc.D., of the University of California Irvine, and colleagues online in Neurology.
These findings from one of the largest epidemiological studies in the oldest-old group suggested that the pattern of dementia changes for men late in life. Yet for women the doubling rate was similar to that in previous studies that typically included patients only up through age 85.
Men in Dr. Corrada's study who reached age 90 were about half as likely to have dementia than women in the same age group, which may have been at least partially because of shorter survival both overall and after dementia diagnosis, the researchers said.
"As the oldest-old are the fastest growing segment of the United States population," they wrote, "accurate estimates of dementia prevalence are crucial for public health planning."
Their population-based 90+ Study followed men and women longitudinally with cognitive assessments starting at age 90. It included 911 participants from the larger Leisure World Cohort Study of a retirement community in Orange County, Calif., initiated in the early 1980s.
The participants were mostly women (77%) and Caucasian (99%). About half of the participants still lived at home (56%), while 16% had moved to a nursing home and 28% to other group quarters.
The age distribution was nearly identical between genders, with an average age of 94.4 among men (range 90 to 105) and 94.5 among women (range 90 to 106).
At entry to the 90+ study, 375 participants (41.2%) had dementia from any cause. The prevalence was significantly lower among men than women (27.6% versus 45.2%, odds ratio 1.97, P<0.001).
The difference between genders carried through most age groups with a dementia prevalence that rose from 27% at ages 90 to 91 to 71% at ages 98 to 99 among women, compared with a fairly stable prevalence among men that rose only slightly from 21% to 33% at age 100 and beyond.
Likewise, dementia risk doubled every five years for women (OR 2.05, P<0.001) but did not rise significantly for men over the same period (OR 1.19, P=0.58).
Even after adjustment for the method with which dementia was determined, age and sex remained linked to dementia prevalence with little change in the odds ratios (P<0.001), suggesting this factor was unlikely to explain the disparity, the researchers said.
The authors did cite the fact that only some of the participants had an in-person evaluation as a limitation of the study.
However, education appeared to account for some of the difference. Women with more than a high school education were 36% to 45% less likely to develop dementia in old age than less educated women. Education was not a significant factor among men.
Dr. Corrada and colleagues speculated that women could have sex-specific dementia risk factors that increase at the end of life to raise incidence compared with men.
"The few men who reach age 90 and beyond may be 'survivors' with fewer risk factors for developing dementia," they said, "suggesting that the incidence of dementia does not increase (or may even decrease) for men over 90."
Another possibility is shorter duration of dementia in men rather than a change in incidence, they said. In addition to shorter survival among men in the general population, several studies have shown shorter survival among elderly men with dementia than among their female peers.
The investigators cautioned that the generalizability of the findings could be limited as the cohort was predominantly white, well educated, and richer.
The study was supported by the National Institutes of Health and the Al and Trish Nichols Chair in Clinical Neuroscience. The researchers reported no conflicts of interest.
Primary source: NeurologySource reference:Corrada MM, et al "Prevalence of dementia after age 90: results from The 90+ Study" Neurology 2008; 71: 337-343.
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