The “Whitehall II Study” was a major piece of research led by experts at University College London (UCL), studying more than 3,000 civil servants up to 14 years before & 14 years after their retirement.
One of the findings, in particular, is pretty sobering for people approaching, or in the early years of retirement.
Declines in verbal memory were 38% faster after retirement compared to before, after taking account of age-related decline.
Higher employment grade was protective against verbal memory decline while people were still working, but this ‘protective effect’ was lost when individuals retired.
The suggestion is that whilst Soduko & other mental exercise may help, the real insurance only comes from keeping mentally active through having an endeavour or venture than comes close to work in terms of mental stimulation.
Some of the references are: