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closeCognitive decline is not the whole story
Posted by JoshuaJArmstrong on 14 May 2013 at 13:21 GMT
Sachdev et al. can be congratulated on this interesting and informative study. With large segments of the global population aging into late-life, it is important that we enhance our understanding of late-life cognition, mild cognitive impairment, and dementia. By focusing on factors that predict so-called “reversion”, the work brings attention that the common account of “relentless progression” of cognitive decline is not the whole story: improvement after experiencing cognitive decline in late-life is possible. This work, in bringing new attention to the phenomenon of reversion from MCI to normal cognitive functioning, supports similar findings elsewhere. For example, several Canadian studies have found similar results1-5. Despite these well documented accounts that cognition in old age is dynamic, still it is dismissed commonly as errors of measurement, instruments, or criteria. Despite the long-held belief of inevitable decline, my opinion is that cognitive improvement in late-life is inherent and your results clearly illustrate this fact.
Reversion from MCI to normal function likely reflects the dynamic nature of physiological systems and the brain; late-life cognition can be heavily influenced by one’s physical state (in addition to other factors). For example,the impact of frailty on cognition in late-life has been illustrated using multistate transition models6,7 where frailty status, as measured by the frailty index, was shown to be significantly predictive of future cognitive states. Future work by our group will continue along this path by looking at the dynamic and interactive relationships between cognition, physical health, and brain health in various large longitudinal data sets. The goal is to add to the understanding of the dynamics of late-life cognition.
References
1. Feldman H et al. A Canadian cohort study of cognitive impairment and related dementias (ACCORD): Study methods and baseline results. Neuroepidemiology. 2003;22(5):265-274.
2. Graham JE et al. Prevalence and severity of cognitive impairment with and without dementia in an elderly population. Lancet (London, England). 1997;349(9068):1793-1796.
3. Hsiung GY et al. Transition from cognitively impaired not demented to alzheimer's disease: An analysis of changes in functional abilities in a dementia clinic cohort. Dement Geriatr Cogn Disord. 2008;25(6):483-490.
4. Hsiung GY et al. Outcomes of cognitively impaired not demented at 2 years in the canadian cohort study of cognitive impairment and related dementias. Dement Geriatr Cogn Disord. 2006;22(5-6):413-420.
5. Tuokko H et al. Five-year follow-up of cognitive impairment with no dementia. Arch Neurol. 2003;60(4):577-582. doi: 10.1001/archneur.60.4.577.
6. Mitnitski A et al. A multistate model of cognitive dynamics in relation to frailty in older adults. Ann Epidemiol. 2011;21(7):507-516.
7. Mitnitski A et al. Transitions in cognitive status in relation to frailty in older adults: A comparison of three frailty measures. Journal of Nutrition, Health and Aging. 2011;15(10):863-867.