One
limitation of these criteria is that they fail to separate with adequate sensitivity and specificity those individuals with true benign cognitive decline from those that will progress to full-blown dementia. Methodological issues Most studies addressing age-related cognitive and ncuroradiological changes have a cross-sectional design, Inhibitors,research,lifescience,medical ie, they examine differences between cohorts of young and elderly healthy individuals at a single point, in time. One limitation of this strategy is the risk of a cohort effect (a cohort is defined as those people within a specific population who experienced the same significant, life events within a given period of time). Thus, clinical differences between young and old groups of individuals
may be more strongly related to different life experiences at certain ages, rather Inhibitors,research,lifescience,medical than to a true age effect. For instance, later-born subjects were reported to perform better on cognitive testing than earlier-born Inhibitors,research,lifescience,medical subjects tested at the same age.16 Longitudinal studies, in which the same group of subjects are examined over time, have a lower risk of cohort effects, but may Forskolin clinical trial suffer from important, attrition, producing skewed samples at, the end of the Inhibitors,research,lifescience,medical study. This may result in a “survivor effect,” ie, a relative overrepresentation of healthier subjects at the end of a longitudinal study.17 Medical conditions with a relatively higher prevalence in the elderly, such as chronic respiratory disorders, cardiovascular disease, and diabetes, may themselves produce cognitive deficits and also influence the results of longitudinal studies. In summary, cross-sectional studies comparing groups of young versus elderly individuals may suffer from a cohort, effect, ie, Inhibitors,research,lifescience,medical differences may result, not.
from a true age effect, but from the effects of membership in different, birth cohorts. On the other hand, longitudinal studies Resminostat may suffer from, both significant, attrition effects and a greater influence of medical problems on cognition among the elderly. Age-related neuropsychological changes The aging process is characterized by a progressive decline in cognitive function, which is illustrated by the fact. that, norms on the Wechsler Memory Scale for individuals over 70 years arc about, 54% lower than those for young adults.6 Salthouse18 found that age explained 17% to 31% of the variance in measures of reasoning in healthy individuals from 20 to 84 years of age. Most of these age-related effects were found on tasks of simple perceptual comparison speed and working memory.