The effect of cognitive leisure (eg reading books, playing cards etc) on prevention of cognitive impairment was studied in 36 adults (31 women) with MS treated at Kessler Research Center, West Orange, New Jersey Medical School, and Teachers College, Columbia University, NY, NY. Cognitive status was measured with a composite score of processing speed and memory, and brain atrophy was measured by third ventricle width on MRI. Controlling for brain atrophy, vocabulary and education, premorbid cognitive leisure was positively associated with current cognitive status (p<0.01). Patients with MS who engaged in more cognitive leisure were able to withstand the effects of more severe brain atrophy. Cognitive leisure is an independent source of cognitive reserve in patients with MS. 
COMMENT. Lifetime intellectual enrichment lessens the adverse effect of neurologic disease (eg Alzheimer disease) on cognitive status.  The present study shows that cognitive leisure time may contribute to cognitive reserve in patients with MS.
The “London taxi driver“ study provides neuroanatomic support for the cognitive reserve hypothesis . The time as a taxi driver (in London) is positively correlated with posterior hippocampal volumes (serving spatial memory). I believe that London taxi drivers were required to study and pass a City address and navigation test to obtain a license. Not an easy task. The term “cognitive toil“ might be more appropriate.