In what may be the first study of this kind, researchers say they found that adults who sleep less than five or six hours a night are four times more likely to catch a cold than than those who get at least seven or more hours of sleep.

“Sleep plays a role in regulating the immune system, and that’s how we think it influences susceptibility to the common cold,” said Aric A. Prather, an assistant professor of psychiatry at the University of California, San Francisco, who is the lead author of the study, published this week in the journal Sleep.

Previous research had suggested a link between less sleep and higher vulnerability to colds, but that study relied on subjects self-reporting the number of hours they slept. The new study was the first to measure actual sleep. To do so, the researchers used a technique called wrist actigraphy, which uses a watchlike device with an accelerometer that measures movement and inactivity and which, when combined with sleep diaries, provides a more accurate accounting of sleep.

“This study reinforces the notion that sleep is just as important to your health as diet and exercise,” said Dr. Nathaniel F. Watson, president of the American Academy of Sleep Medicine. “People need to view sleep as a tool to achieve a healthy life, rather than as something that interferes with all their other activities.”

Many Americans don’t get enough sleep; a 2013 survey by the National Sleep Foundation said that one in five adults gets less than six hours of sleep on an average work night.

Poor sleep has been linked to numerous chronic illnesses, and new guidelinesissued this year by the American Academy of Sleep Medicine and the Sleep Research Society urge adults to get seven or more hours of sleep per night on a regular basis to promote optimal health.

The guidelines say that sleeping less than seven hours per night is associated with weight gain, diabetes, hypertension, heart disease and stroke, depression and premature death, as well as “impaired immune function, increased pain, impaired performance, increased errors and greater risk of accidents.”

The new study recruited 164 men and women aged 18 to 55 from the Pittsburgh area between 2007 and 2011, and put them through extensive health screenings, questionnaires and interviews to determine their levels of stress, their general temperament and their use of alcohol and tobacco. Then the researchers measured the subjects’ normal sleep habits for a week, before sequestering them in a hotel and deliberately administering them nasal drops containing the cold virus.

The volunteers were monitored for a week and daily mucus samples were collected to see if they had become infected.

Those who slept less than six hours a night the week before the exposure were 4.2 times more likely to catch the cold compared with those who got more than seven hours of sleep, researchers found. Those who slept less than five hours a night were 4.5 times more likely to catch the cold. (Those who slept just over six hours but less than seven weren’t at increased risk.)

It didn’t seem to matter whether the sleep was continuous or fragmented, Dr. Prather said. The results were adjusted to control for differences among subjects, including pre-existing antibody levels to the rhinovirus, age, sex, race, body mass index, the time of year when the trial was done, education, income, health habits such as smoking and physical activity, and psychological variables such as stress.

“The good thing about this is that there are opportunities for people to improve their sleep, and most people admit they need more and want more,” Dr. Prather said, adding, “it’s just about looking at the barriers and making it a priority.”