Regardless of other risk factors, people who don’t sleep enough face an increased threat of cardiovascular disease (CVD), the leading killer of American men and women. In fact, one study of about 3,000 people over the age of 45 reported that those who snoozed fewer than six hours a night were twice as likely to suffer a heart attack or stroke as people who slept six to eight hours a night, according to the National Sleep Foundation.

But why does skimping on slumber have such a dramatic effect on heart attack and stroke risk? Research suggests that lack of sleep has adverse effects on blood pressure, inflammation, weight, and the body’s ability to metabolize glucose (blood sugar). Here are some important discoveries about sleep and heart health.

  • Snoring can be a warning sign of increased heart attack and stroke risk. Loud, persistent snoring is a common symptom of obstructive sleep apnea (OSA), an often-undiagnosed sleep disorder that has been shown in several studies to double risk for stroke, heart attack or other cardiovascular events. The good news is that if OSA is treated, the excess risk can be eliminated, a recent study found. Treatment may include using a CPAP (continuous positive airway pressure) machine.
  • If your blood pressure medication isn’t working, a sleep disorder could be the problem. Undiagnosed OSA is a common cause of hypertension that doesn’t respond to prescribed medications. If you fit this scenario, talk to your medical provider about having a sleep study, even if you think you don’t snore, since many people with OSA are unaware of their symptoms, which can also include frequently waking up in the night and daytime drowsiness.
  • Sleeping fewer than six hours a night more than quadruples risk for pre-diabetes! When researchers tracked 364 people for a six-year period, those who averaged fewer than six hours of shut-eye were 4.7 times more likely to develop impaired fasting glucose (also known as pre-diabetes) than those who got more sleep, even when other factors, such as family history of diabetes or weight gain, were taken into account.
  • Sleeping 7 to 8 hours a night may be ideal for weight control. Compared to people who slept 7 to 8 hours a night, those who slumbered 5 to 6 hours were 27% more likely to become obese, according to a six-year study. The researchers also found that people who averaged 9 to 10 hours of shut-eye a night had 21% rise in obesity risk. One theory is that sleep duration may influence levels of the hormones leptin and ghrelin, which regulate appetite.
  • Sleeping too little–or too much–nearly doubles stroke risk in people with high blood pressure. Hypertension is the leading risk factor for stroke and a major contributor to heart disease. In a study of 200,000 people with high blood pressure, those who snoozed fewer than 5 hours a night were 1.83 times more likely to suffer a stroke than those who slept 7 to 8 hours. Sleeping more than 8 hours a night raised stroke risk by 74%.
  • Regular exercise can dramatically improve sleep quality. In a study of more than 2,600 adults, those who got at least 150 minutes of moderate-to-vigorous physical activity a week, as advised by national guidelines, reported a 65% improvement in the quality of their sleep–and felt less drowsy during the day–than people who exercised less. Before starting a new fitness regime, check with your medical provider to make sure it is appropriate for you.