Americans certainly aren't strangers to putting in long hours on the job. An estimated 40% of U.S. employees typically work more than 50 hours per week, while 20% work more than 60. But even if you don't put in that amount of time, chances are you adhere to the standard 40-hour workweek. After all, that's the amount of time needed to ensure the best possible performance, right?

Maybe not.

It turns out working fewer hours might produce better results at the office. In a study conducted by the Melbourne Institute of Applied Economic and Social Research, 6,000 workers over age 40 were observed to see how the number of hours they worked in a given week would impact their cognitive ability. The results? Folks over 40 were better off working somewhere in the 22- to 27-hour range on a weekly basis, and not the 40 hours or more corporate America tends to demand.

Man at laptop holding head.

IMAGE SOURCE: GETTY IMAGES.

Specifically, optimal working hours for men over 40 are 25 to 30 per week, according to the aforementioned study. For women over 40, it's 22 to 27. Those who put in more time than that face cognitive challenges that could impact their ability to process information and perform well on the job. And that's certainly a good reason to cut back.

Quality of work over quantity of time

There's a reason employers often mandate a certain number of hours during the workweek: to be consistent while ensuring that key tasks get done on schedule. But the fact of the matter is that different people work at different paces, and what one person accomplishes in three hours might take another person seven or eight. It therefore builds the case for companies to adopt a different approach to employee scheduling: to focus on quality of work versus hours spent in an office chair.

And this holds true regardless of age. In fact, to implement age-based policies would open the door to a host of legal issues that are best avoided.

Of course, it's somewhat unlikely that companies will get on board with the idea of the standard 25-hour workweek, even if research continues to suggest that longer hours hurt productivity rather than help it. But if you're tired of maintaining a preset schedule just because it's company policy, you might approach your manager and ask for a little leeway, especially if you're a consistent performer who's never missed a deadline.

Meanwhile, middle-aged workers should take note of the fact that age 40 is when people's performance on memory tests and other mental agility exercises can start to drop. This isn't to say that it will happen to you, but if you find that you're constantly burning the midnight oil at work yet aren't accomplishing more, consider it a sign that you need to cut back. Doing so might not only improve your performance but prevent burnout and mental health issues associated with excessive levels of work. And that's something you want to avoid at any age.

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