A new study has discovered that the people who don’t sleep enough might be at risk to form calcium deposits in their coronary arteries and develop heart disease. The study tracked 495 volunteers who filled up questionnaires about their sleep habits. During the study, they also kept a log of their hours spent in bed.

During the night they wore motion-sensing devices on their wrists as to estimate the number of hours they spent sleeping. None of the 495 participants aged between 35 and 47 had coronary artery calcification at the beginning of the study. But after five years 27% of them were found to sleep less than five hours during a night. Thus, they developed coronary artery calcification for the first time.

Yet, only 6% of them used to sleep seven hours a night but they had also developed the calcium deposits. All in all, the study found that 11% of those who used to sleep between five and seven hours a night developed coronary artery calcification. The researchers also concluded that one hour of sleep a night was linked to 33% decrease in the calcium deposits development.

Diane S. Lauderdale, the author of the study and an associate professor of health studies at the University of Chicago Medical Center, added that this study doesn’t represent a relationship of cause and effect between the lack of sleep and heart disease. The data published in the article from the Journal of the American Medical association was taken from the new Coronary Artery Risk Development In Young Adults study.

Lauderdale aAdded that it’s important for people to know that this is the first report released on this issue and that this doesn’t prove “the association is causal.” She also said that the team taking care of this problem has to first find out about the mechanism causing these effects before releasing recommendations “based on this.”