Entrepreneurs frequently complain about sacrificing their health to the business. Big mistake.

It turns out that exercise can actually improve brain functioning. In a recent study published in the journal Neuroscience, researchers compared mice that lived in a cage with a running wheel with mice housed in an empty cage; a cage filled with toys and food; and a cage filled with toys, food, and a wheel. Within a month, the mice in the running-only group were crushing their peers in cognitive tests. Those mice also showed growth in the hippocampus, a part of the brain that's critical to learning and memory and that shrinks with age.

Aerobic exercise can be particularly helpful as you age. In a 2011 study led by the University of Pittsburgh's Kirk Erickson, 120 older adults were assigned to either walk on a track three days a week or participate in toning exercises.

After a year, hippocampal volume had increased 2 percent in the walking group. The other group experienced the standard shrinkage associated with age. Aerobic exercise, the study concluded, reversed at least some of the effects of aging on the brain.

There's more to health than exercise, of course.

Research suggests that lower out-of-pocket health care costs tend to make employees more productive. In September, researchers from the University of Michigan and Harvard Medical School published a study on health care costs and employee absenteeism. Using a national database of insurance claims for 25,000 employees being treated for chronic pain, as well as absentee data provided by employers, the researchers found a direct correlation between higher costs to the patient and work hours lost.

For every $5 increase in health care costs incurred by employees, absences increased by one hour. The authors speculate that the higher the costs, the fewer prescriptions employees filled, so they experienced more pain and missed more days of work.

Although the study doesn't entirely prove causation, its findings should interest you if you're wondering whether you can afford to cover health benefits for your employees.