Samsung Galaxy S4
Samsung Electronics' Galaxy S4 (L) and Apple's iPhone 5 are seen in this file picture illustration taken in Seoul. REUTERS / Kim Hong-Ji

Employees addicted to smartphone use even into their bedtime are ought to kick the habit. A study released by University of Washington showed that while smartphones may be useful for a lot of things, it may post some risks to one's sleep patterns.

"Smartphones are enormously valuable for helping people to fit work activity into times and places outside of the office," Christopher Barnes, assistant professor of management at the Foster School of Business and lead researcher, said in a statement.

Samsung Electronics' Galaxy S4 (L) and Apple's iPhone 5 are seen in this file picture illustration taken in Seoul on May 13, 2013. Samsung Electronics Co Ltd is bracing for its weakest smartphone profit growth in 2014 since 2007 as arch rival Apple Inc challenges its domination in China's $80 billion market. REUTERS/Kim Hong-Ji/Files

"But greater connectivity comes at a cost," he added. "Using a smartphone to cram more work into a given evening results in less work done the next day."

Being continuously engaged to one's smartphone at night hinders a good night's sleep greatly affecting an employee's efficiency the next day. If one's mind is sleepy, it can hardly focus on the task at hand, much more finishing it.

"Employees need to start their day working on a fresh brain. They obviously won't be able to do this if they feel drained even after waking up from sleep," Barnes noted.

According to Australia's Sleep Health Foundation, getting fewer than 8 hours of sleep compromises alertness, reaction time, efficiency, productivity and mood.

The group said it would be best that employees switch off their devices by 9 p.m. It likewise advised employee bosses should be considerate enough to let their staff rest. "Bosses should make sure to send e-mails in the morning rather than in the night."

"The more important the job, the more important it is to work with a fresh brain," the University of Washington researchers said.

According to IBISWorld, from 2008 to 2011, revenue from clinics treating sleep disorders in the U.S. had increased to 12 percent per year to $6 billion.