http://www.medpagetoday.com/Geriatrics/Dementia/30523
- Explain that the cognitive decline associated with aging begins earlier than has been appreciated, with changes already evident in the fifth decade of life.
- Point out that on all of the cognitive measures except vocabulary, which typically remains unaffected with age, linear trends were seen in decline, with greater changes seen in those who were older at baseline.
The cognitive decline associated with aging begins earlier than has been appreciated, with changes already evident in the fifth decade of life, a prospective study showed.
The ten-year decline in reasoning ability among men who were ages 45 to 49 at baseline was −3.6% (95% CI −4.1 to −3), according to Archana Singh-Manoux, PhD, of University College London, and colleagues.
Women of that age also showed a decline of −3.6 (95% CI −4.6 to −2.7), the researchers reported online in BMJ.
It has previously been suggested that cognitive decline was minimal before age 60, but this point of view has not been universally accepted, the authors said. Research has shown pathologic changes associated with dementia in young adult brains, while emerging consensus on the long gestation period of dementia has indicated that adults under 60 are likely to experience age-related cognitive decline, they added.
To explore this possibility, which is increasingly important as life expectancy extends, Singh-Manoux and colleagues analyzed data from the Whitehall II cohort study, which was initiated in 1985 and included more than 10,000 British civil servants.
This analysis included 5,198 men and 2,192 women, most of whom were white and married.
Beginning in 1997, participants underwent cognitive testing three times at five-year intervals to evaluate reasoning, memory, phonemic and semantic fluency, and vocabulary.
On all of these measures except vocabulary, which typically remains unaffected with age, linear trends were seen in decline, with greater changes seen in those who were older at baseline.
For instance, in men who were 65 to 70 at baseline, the ten-year decline in reasoning was −9.6% (95% CI −10.6 to −8.6), which was significantly greater than the decline seen in those who were 45 to 49 at baseline (P<0.001).
Among women ages 65 to 70 at baseline, the decline was −7.4% (95% CI −9.1 to −5.7), which also was significantly greater than in the youngest group (P<0.001).
The researchers also compared these longitudinal data with cross-sectional findings, which some other authors have recommended as a simpler way of tracking aging effects, and found that the cross-sectional analysis overestimated the cognitive effects of aging, particularly in women.
While in the longitudinal analysis, the decline in reasoning among women ages 45 to 49 was −3.6%, the cross-sectional analysis estimated the decline to be −11.4% (95% CI −14 to −8.9).
This difference was likely to be related to cohort differences in education over time among women, the researchers suggested.
Among women who were 45 to 49 at baseline, 34% had less than a high school education, 28% had completed high school, and 40% had a college degree.
But among those who were 55 to 59 at baseline, the corresponding numbers were 58%, 25%, and 17%.
"Cohort effects are produced when a birth cohort enters adult life with long lasting effects on cognitive function because of childhood experiences like quality of education, nutrition, socioeconomic circumstances, etc.," the researchers explained.
The findings of this study have important clinical implications, because there is increasing evidence for the importance of lifestyle factors and cardiovascular risk in middle age on later life cognitive function.
Mid-life risk factors such as hypertension, obesity, and dyslipidemia appear to be particularly influential.
"There is emerging consensus that 'what is good for our hearts is also good for our heads,' making aggressive control of behavioral and cardiovascular risk factors as early as possible key targets for clinical practice and public health," Singh-Manoux and colleagues wrote.
Future research needs to focus on identifying specific modifiable risk factors that could be targeted at younger ages.
"Determining the age window at which potential interventions are likely to be most beneficial is also a crucial next step," they observed.
In an accompanying editorial, Francine Grodstein, DSc, of Harvard Medical School in Boston, agreed about the importance of early intervention.
"As yet, there is no cure for dementia, and accumulating evidence indicates that effective interventions will need to be administered long before marked neurodegeneration has occurred," Grodstein wrote.
She pointed out that research into the effects of aging on cognition will need to involve very large populations, and that data collection will need to be adapted accordingly, such as through the use of telephone and computer surveys and assessments.
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