Given a choice, most people would skip work and relax, spend more time with family or enjoy their favorite hobby; and who wouldn't? But unless you are filthy rich, that option is not in the cards for you. Fortunately, that's not something most people have an issue with, holding down a job is even considered a source of pride. Besides, most people would not know what to do with themselves without a regular job.

But a study says that you should start slowing down once you are 40 years. Although age will improve your knowledge and make you more composed as you work, it will also bring with it some serious downsides that begin to set in once you are 40 years of age.

You will not be completely useless as a worker at this age, obviously. But the youthful energy and impulse that had you breeze through a demanding workweek without showing any negative effects will no longer be with you. This has been confirmed through a broad and extensive study on the subject.

The Australian study has shown that past this age, your best performance is possible when you put in three days of work per week, not five. The study involved 3,000 men and 3,500 women over forty years of age. According to this study, a 30 hour week is just perfect for those over 40 years. In fact, for people over 55 working for more than 30 hours, there was even a cognitive decline that exceeded that of those who were not working.

Work, as it turns out, is a double-edged sword. Too much of it can cause a decline in cognitive abilities. On the other hand, an appropriate amount of work helps enhance cognitive capabilities. A 30-hour week helps provide this positive cognitive stimulation for individuals who are above 40 years of age.

The findings of this study are a mixed bag at a time when people are being encouraged to spend more of their lives working. Many governments are raising the age at which workers are eligible for a pension, which means people will have to work for much longer even after their forties in order to get their pension.

But the truth is that working so hard after the age of forty can do serious damage to individuals and their productivity. In addition to witnessing a decline in work performance, working for too many hours after the age of forty also means dealing with more pronounced cognitive problems.

So, governments and corporations that are in a position to do something about this issue could lower the number of hours their older employees put in at work for the sake of their efficiency and cognitive health.