Watching the clock edge slowly towards quitting time is more than just boring — it can be setting you up for memory loss in your senior years, especially if your working environment is also dirty.

A new study at Florida State University found that both a lack of stimulation in the workplace combined with a dirty working environment can have a long-term cognitive effect on employees.

"Psychologists say that the brain is a muscle, while industrial hygienists point to chemicals in the work environment that may cause decline," said lead researcher Joseph Grzywacz.

"There are real things in the workplace that can shape cognitive function: some that you can see or touch, and others you can't. We showed that both matter to cognitive health in adulthood."

Before the study, researchers couldn't agree on whether a dirty working environment with exposure to mold, lead or loud noises took the biggest toll on brain health as people aged, or simply working in a dull environment that lacked stimulation.

This new study showed both can be important in long-term brain health: Researchers found that the more a job involved learning new skills and taking on new challenges, the stronger the cognitive performance, especially for women, as workers aged.

The study also found that both men and women who had jobs that exposed them to a dirty working environment saw a cognitive decline.

"Both of these issues are important when we think about the long-term health of men and women," said Grzywacz.

Grzywacz and his colleagues analyzed the data from 4,963 adults ages 32 to 84. They examined the participants' workplaces and their ability to maintain and later use information they learned. They also looked at their executive functioning skills such as their ability to complete tasks, manage time, and pay attention. Additionally, the data included responses from participants asking them about any memory issues they were experiencing.

"The practical issue here is cognitive decline associated with aging and the thought of, 'if you don't use it, you lose it,'" Grzywacz said. "Designing jobs to ensure that all workers have some decision making ability may protect cognitive function later in life, but it's also about cleaning up the workplace."

The study is published in the June issue of the Journal of Occupational and Environmental Medicine.