According to a study by Timothy A. Salthouse, PhD, at the University of Virginia in Charlottesville, a reduction in cognitive function begins in individuals late 20s. Using cross-sectional, longitudinal, and short-term restest frameworks over a 7-year period, Salthouse and colleagues recruited 2,350 patients from newspaper advertisements, flyers, and referrals from other participants. They ranged between 18-60 years of age and were tested individually. Additional data were acquired from previous studies by Salthouse and colleagues. Many of the participants in Salthouse's study were tested several times during the course of years, allowing researchers to detect subtle declines in cognitive ability. Among the variables analyzed were vocabulary, memory, and reasoning. Measures included the Wechsler Adult Intelligence Scale III. Highest ratings on scales were achieved at 22 years of age, with a reduction in some measures of abstract reasoning, brain speed, and in puzzle solving noticeable at 27 years of age. Average memory declines can be detected at ~37 years of age. Nevertheless, accumulated knowledge skills, such as improvement of vocabulary and general knowledge, actually increase at least until 60 years of age. This implies that cognitive decline is not static across the general population. "These patterns suggest that some types of mental flexibility decrease relatively early in adulthood, but that how much knowledge one has, and the effectiveness of integrating it with one's abilities, may increase throughout all of adulthood if there are no pathological diseases," Dr. Salthouse said. Salthouse and colleagues are continuing research in the same cohort in order to determine whether social relationships, serve to moderate age-related cognitive changes. "By following individuals over time, we gain insight to cognition changes, and may possibly discover ways to alleviate or slow the rate of decline, and by better understanding the processes of cognitive impairment, we may become better at predicting the onset of dementias such as Alzheimer's disease," Dr. Salthouse said.