People who skip sleep hours or reduce them become more prone to calcifications in their coronary arteries. This can increase their risk for heart disease.

A research was conducted on 495 participants. The participants were asked to fill a sleep questionnaires and keep a track of their sleeping hours. They were also asked to wear a motion-sensing devices around their wrists at night. The device estimated the number of hours of actual sleep. At the beginning, none of the participants, who were ages 35 to 47, had evidence of coronary artery calcification.

After five years, 27 percent of those had less than five hours sleep on average had developed coronary artery calcification. On the other hand only 6 percent of those who were sleeping seven hours or more had developed it. Among those who were sleeping between five and seven hours a night, 11 percent had developed coronary artery calcification.

There was a possible link between calcification and lack of sleep. The risk was lowest for those who regularly had more than seven hours sleep each night.

Lead researcher Dr Diane Lauderdale, of the University of Chicago, said they had been able to find many explanations for the link between calcification and sleeplessness. But at the same time she also commented that the report does not establish any cause-and-effect relationship between the two.