People with poor sleep habits may have an increased risk of heart disease, according to a recent study.

Korean researchers found that people who got too much, too little or low quality sleep may experience "the beginnings of hardening of the arteries," which is an early sign of heart disease, Reuters reported.

"Many people, up to one third or one fourth of the general population, suffer from inadequate sleep - either insufficient duration of sleep or poor quality of sleep," Dr. Chan-Won Kim, co-lead author of the study, told Reuters Health.

For the study, researchers collected and analyzed data from more than 47,000 young and middle-aged adults who completed a sleep questionnaire and had advanced tests to detect early coronary artery lesions and measure arterial stiffness. Early coronary lesions were detected as the presence of calcium in the coronary arteries and arterial stiffness was assessed by measuring the velocity, or speed, of the pulse wave between the arteries in the upper arm and ankle.

They found that adults who sleep five or fewer hours a day have 50 percent more calcium in their coronary arteries than those who sleep seven hours a day, Medical Daily reported. Researchers also found that those who sleep nine or more hours a day have more than 70 percent more coronary calcium compared to those who sleep seven hours. Additionally, adults who reported poor sleep quality had more than 20 percent more coronary calcium than those who reported good sleep quality.

"We also observed a similar pattern when we measured arterial stiffness," Yoosoo Chang, study co-lead author and associate professor in the Center for Cohort Studies at Kangbuk Samsun Hospital, said in a statement. "Adults with poor sleep quality have stiffer arteries than those who sleep seven hours a day or had good sleep quality. Overall, we saw the lowest levels of vascular disease in adults sleeping seven hours a day and reporting good sleep quality."

The study's findings, which are detailed in the journal Arteriosclerosis, Thrombosis and Vascular Biology