6 Schretlen et al24 reported that age-related cognitive deficits are more pronounced on tasks that involve on-line problem, solving and visuospatial information
processing (also known as “fluid” spatial abilities) compared with tasks that involve overlearned knowledge and skills (also known as “crystallized” verbal abilities). There are several longitudinal studies of cognitive decline in cohorts of young and old adults. Mortenscn and Kleven25 used the Wechsler Adult, Intelligence Scale (WAIS) to examine a random sample of healthy individuals 50 years of Inhibitors,research,lifescience,medical age at. the time of the initial evaluation, who had repeated evaluations 10 and 20 years later. They found a slight. (3-point) decline on verbal IQ and a 7 point decline on performance IQ.The Seattle Longitudinal Study26 Inhibitors,research,lifescience,medical examined a series of 500 healthy individuals
between 21 to 70 years of age every 7 years, and found an earlier decline in fluid than in crystallized cognitive abilities. The Baltimore Longitudinal Study of Aging27 assessed a series of healthy individuals between 30 and 80 years of age every 6 years. Tlicy found age-related declines in memory tasks, but minimal changes on tests of crystallized intelligence. Inhibitors,research,lifescience,medical The Duke Longitudinal Study of Normal Aging28 assessed 267 healthy community-dwelling Inhibitors,research,lifescience,medical individuals between 60 to 94 years of age. After a mean follow-up of 21 years, there were significant declines in verbal IQ, performance IQ, and performance on visual, but, not verbal, memory tasks. The Bonn
Longitudinal Study of selleck compound Aging29 assessed cohorts of healthy individuals between 60 and 65 years of age and 70 and 75 years of age, during a 12-year period. They found a significant, 5point drop in verbal IQ for the older but not for the younger cohort; similar results were obtained on tests assessing psychomotor and executive functions. The Health and Lifestyle Survey16 assessed more Inhibitors,research,lifescience,medical than 2000 healthy individuals 7 years apart. They found no significant, changes in tasks of motor reaction time, visuospatial reasoning, and memory until the fifth decade, but, there was a marked decline in all three tasks for individuals above 75 years of age. Snowdon and Lane30 assessed 146 healthy subjects aged 65 to 95 years, 8 years apart. They found that about 50% of the individuals with a diagnosis isothipendyl of AAMI improved their cognitive performance during the follow-up period. Laursen31 assessed four successive age cohorts born in 1952, 1942, 1932, and 1922 on two occasions with an interval of about 10 years. There were significant, declines in spatial and verbal memory, visuo motor and visuospatial speed, concentration, and motor reaction time, but the overall cognitive decline was mild and of dubious clinical significance.