> My completely-devoid-of-evidence hypothesis is that over the past 25 years, increased globalization has reduced the number of menial jobs/tasks in those two c

> My completely-devoid-of-evidence hypothesis is that over the past 25 years, increased globalization has reduced the number of menial jobs/tasks in those two continents, thereby increasing overall day-to-day mental exercise. This fails on a couple levels to explain the headline: 1. 25 years is a very short time for someone to have a health-altering period of employment and then get old enough to develop dementia. The overall population with dementia is much larger, so in order to see a 13% drop, the final <10 years of work before you retire would need to increase your risk of dementia by several times. 2. It does not make sense that those people who are within 25 years of dementia would be able to suddenly switch from a menial job to an intellectual job. I would guess it is very unlikely (<10%) over any time horizon; the western world switched from manual jobs to service jobs but it's very difficult for people in those two categories to return to school and get an intellectual job. 3. I would hazard to guess that manual jobs are more intellectually stimulating than most service jobs. Working in a factory, building houses etc. includes tons of little bits of arithmetic and coordination. Phone/computer jobs and working in a store is mostly standing around or doing mind-numbing makework. At the very least, there's not a huge difference between the two- besides physical work, which is also very beneficial against dementia.