Email overload may be doing more than driving you crazy -- it could be sending you to an early grave. Research from the University of California at Irvine and the U.S. Army found that study subjects with access to email remained in a continual state of "high alert," with constantly elevated heart rates. In contrast, subjects who didn’t have email access have more natural, varied heart rates.

People with email access multitasked twice as much as those without, measured by how often they changed computer screens (37 times per hour compared to 18 times per hour). Subjects with no email said they are better able to do their jobs and stay on task and experience fewer stressful and time-wasting interruptions. Instead of answering emails, they interact with co-workers in person, which makes them happier. The researchers also believe the physical act of getting up and walking also provides stress relief.

Why it matters to your business: Continually elevated heart rates are linked with the production of cortisol, a hormone that causes multiple health problems. You can't unplug yourself or your employees from email for five days, but consider tactics such as batching messages, checking email only at certain times of day or designating one day a week as an "email vacation." You'll be rewarded with increased productivity AND better health.