JUST 20 minutes a day.
Eleven participants received weekly, hour-long memory training sessions and performed exercises ranging from crossword puzzles to computer-based tasks.
The other 14 were given an hour-long yoga session once a week and practised Kirtan Kriya meditation at home for 20 minutes each day.
The form of yoga used in the study, known as Kundalini, focuses on breathing, meditation and chanting as well as poses designed to increase strength and flexibility.
It incorporates Kirtan Kriya meditation, which involves chanting, hand movements and visualisation of light, and has been used for centuries in India to prevent mental decline in older adults.
After 12 weeks, the scientists saw similar verbal memory improvements in both groups.
However, visual-spatial memory was increased to a greater degree in the yoga-meditation group.
Participants practising yoga and meditation were also less likely to be depressed and anxious, and were better able to cope with stress.
Mood enhancement is important because of the emotional difficulties involved in coming to terms with cognitive impairment, said the researchers.