In the Time Magazine article "Study: Cognitive Decline Sets In as Early as Age 45," a group of researchers from France and England used the data from the Whitehall II Cohort, a study of 10,308 British civil servants medically and socially since 1985, to identify the beginning of loss in cognitive skills. This study was started by Professor Sir Michael Marmot and sponsored by a variety of organizations including the Medical Research Council, the National Institute of Aging, and the MacArthur Foundation in order to research social and occupational influences on health and illness. These sponsors were interested in contributing funds to the study because it was developed as a wide-ranging study that included information on all aspects of the participants' lives along with medical exams. By contributing, the sponsors stood to gain any new knowledge that could lead to breakthroughs in the medical and psychology fields. The study was conducted between five age groups: 45-49, 50-54, 55-59, 60-64, and 65-70. This was done to monitor the progression or regression of any skills as the participants grew older. As a result of this control group, the results are communicated well and are understandable due to the conclusion. This is further supported by the easily readable graphs, which show the decline of cognitive skills for both men and women as they grow older.
Blue, Laura. "Study: Cognitive Decline Sets In as Early as Age 45", Time Magazine, Time Healthland, January 8, 2012. http://healthland.time.com/2012/01/06/study-cognitive-decline-sets-in-as-early-as-age-45/
British Medical Journal
Whitehall II Cohort