After decades of poking and prodding patients at all hours, hospitals are waking up to the notion that sick people need sleep.

At least one Raleigh, N.C., area health system — WakeMed Health & Hospitals — now observes nightly quiet hours at its facilities starting at 8 p.m.

Several intensive-care units at hospitals across the region offer daily quiet time. Lights are dimmed, the volume on the overhead paging system comes down and routine care is scheduled before or after the break. Patients get two hours of undisturbed rest.

It’s a welcome peace amid the persistent activity in the ICU, where nurses or other medical staff sometimes come to the bedside as often as every 20 minutes. Factor in chatter around the nurses’ station, the intercom’s blare and the constant rumble of gurneys and supply carts, and shut-eye is next to impossible.

“Many patients are relieved to know that they’re going to have two hours where no one’s going to come and talk to them,” said Dorothy Taylor-Senter, clinical operations director in Duke Hospital’s neurointensive care unit, which pioneered the idea of ICU quiet time in the late 1990s.

Hospitals once were as hushed as libraries, with signs posted to encourage quiet. Now they are bustling 24-hour nerve centers, with ambulances screaming into the emergency department around the clock. Health-care workers are so used to the din they often don’t realize the impact on patients, said Tina Dennis, a clinical nurse specialist at WakeMed’s main hospital in Raleigh.

Sleep deprivation can stimulate stress hormones, suppress the immune system and spur unhealthy changes in blood pressure and other vital signs.

Earlier this year, Dennis took sound measurements in WakeMed’s Raleigh neurointensive care unit and was stunned to find that, at times, the noise level rose to 80 decibels — as loud as a heavy truck in traffic. And that was around patients who had suffered stroke or brain injuries.

“Think of a Mack truck driving through the ICU — not good,” said Dennis.

Dennis is leading a study at WakeMed to see whether giving patients in the neurointensive care unit a daily dose of peace and quiet encourages sleep. Recently, the unit started quiet hours between 2 p.m. and 4 p.m. each day. Patients enlisted for the study will be observed to see whether the daily break indeed results in more slumber.

Over the past several years, hospitals across the country have taken up quiet time as a way to improve patient care and satisfaction.

The Institute for Healthcare Improvement, a Boston nonprofit, encourages hospitals to observe quiet hours. It’s most often seen in ICUs, but some obstetrical floors now give new mothers two-hour quiet periods, to bond with baby, breastfeed or just sleep.