A study has suggested lifelong exercise is the key to keep one\'s brain healthy into the old age. In the study by King\'s College London (KCL), scientists proved how people who keep fit as a child and adult, through activity three or four times a week, improve dramatically cognitive functioning at 50, Daily Express reported. It found even training just one day a week offered major benefits. \"Exercise is a key component to prevent cognitive decline, cardiovascular disease, diabetes and cancer, so public health interventions to promote lifelong exercise have the potential to reduce the personal and social burden associated with these conditions,\" said KCL\'s Alex Dregan. In the study, published in the Psychological Medicine journal, researchers examined levels of exercise at the ages of 11, 16, 33, 42, 46 and 50 in over 9,000 people. The ones exercising weekly as a child and an adult performed better on tests of memory, learning, attention and reasoning at 50 in comparison to those exercising twice or thrice a month.