You've probably read several articles about the risks we face when thinking about retirement, from outliving our money to paying for health care to losing it all in a recession. 

It's the kind of news that can easily make you worry, even if you've been planning diligently for years. Will you be able to retire and afford not just your expected lifestyle, but the unexpected costs that might go along with aging? It's an uncomfortable question, and the answer often seems to be simple: You'll probably need either more savings or more income. 

One way to get both is to keep working past retirement. You may be groaning, but there is evidence that work might be good not just for your wallet but also good for you as a person.  

The chance to grow and change 
There is, of course, the obvious reason for working: You can use any income earned to fund your lifestyle or pad your savings.

But there are also other reasons that might make work the right decision for you. 

For one, 58% of working retirees surveyed by Merrill Lynch considered their retirement a chance to go into a new line of work to pursue a more fulfilling, flexible, or fun career. 

These retirees also overwhelmingly believe that working "helps people stay more youthful" -- over 80% agreed with the statement -- and 66% believe that not working leads to declines in mental and physical strength. 

In other words, retirement work might be something of a fountain of youth.

Retirement and your brain 
There is evidence to back up the relationship between retirement and aging.

For example, a study looking at the U.S. and 12 other countries found that taking an early retirement had a "significant negative impact" on the mental functioning of retirees in their early 60s. 

A study in the UK found that "an active cognitive lifestyle" keeps retirees in better intellectual shape, and yet another found that people who had more engaging jobs before retirement declined more slowly than others.  

While it's hard to formalize a direct link between retirement and aging or working and youthfulness, you can see where the research points. Keeping intellectually active and busy might not only add income to your retirement, but it might also very well help you enjoy a better retirement. 

Rethinking the meaning of retirement
As a retiree, work doesn't have to mean a stressful full-time job. The beauty of age, experience, and presumably a measure of financial security -- whether from reduced expenses or income from Social Security, your 401(k), or a pension -- is that you have the ability to be a little bit more creative in structuring your working life. 

Maybe it's a part-time job at a nice firm, or a position with a non-profit you care deeply about. Perhaps it's even freelancing, consulting, or starting your own business. Taking your work life into your own hands can free you up to pursue the kind of meaningful work that satisfies not just your lifestyle, but also your mind.