A new research study has suggested that people who sleep for six hours or less than six hours a night are more vulnerable to catching cold than those who sleep for more than seven hours a day, Canada am reports.

Earlier studies have linked proper sleep to good health and regulation of T-cell levels, while poor sleep is linked to illnesses, disease susceptibility and even premature death.

The study is called "Behaviorally assessed sleep and susceptibility to the common cold," and appeared online and in the September issue of the journal Sleep.

The researchers specified that the results were the same for people of all ages and did not modify due to changes in stress levels, race, education or income.

For the study, the researchers observed 164 volunteers from the Pittsburgh, PA, between the years 2007 and 2011. The researchers screened the volunteers for two months with health check ups, interviews and questionnaires to ascertain their stress levels, temperament and alcohol and cigarette use.

The researchers also evaluated the normal sleep patterns of the participants' a week before administering the cold virus, using a sensor to measure the quality of their sleep. The researchers were then kept in a hotel, and checked to see if the cold virus had taken hold.

It was found that participants who had slept less than six hours a night had a 4.2 times higher risk of catching the cold than those who slept more than seven hours. Those who slept less than five hours were 4.5 times more likely to catch the cold.