Benjamin Franklin wrote, in Poor Richard's Almanack, "Early to bed, early to rise makes a man healthy, wealthy and wise."
Now a study suggests that Franklin's famous quote might carry more truth than previously thought. It turns out that burning the midnight oil may carry significant heart risks -- even if you're getting a full night of sleep.
According to a new study presented at the American College of Cardiology's 58th annual Scientific Session in Orlando, Fla., men who went to bed after midnight had significantly more arterial stiffening -- an early stage of heart disease -- than those who turned in before midnight, even if the night owls clocked at least seven hours of sleep.
Previous research has revealed the importance of a good night's sleep for maintaining heart health, but the researchers from the Misao Health Clinic in Gifu, Japan, sought to explore whether a late or early bedtime affected heart risk as well.
Lead researcher Dr. Yu Misao of the Misao Health Clinic and colleagues looked at 251 healthy male workers younger than 61 who had an annual checkup that documented their blood pressure, weight, body mass index (BMI), waist circumference, blood pressure and cholesterol levels. Researchers also examined the men's arteries for signs of heart disease and used a questionnaire to assess the men's daily sleep patterns, including sleep duration and average bedtime.
The men were then divided into three groups according to the number of hours they reported sleeping each night: less than six hours, six to seven hours or seven hours or more. In each of these groups, men who reported bedtimes before midnight had healthier arteries than those who said they usually turned in after midnight.
Although Misao said his study does not attempt to answer why an earlier bedtime would reduce one's heart risk, many researchers believe these findings make perfect sense.
"It makes total sense that being fatigued and exhausted is not a good, heart-healthy thing," said Dr. Chip Lavie, medical director of preventive cardiology at the Ochsner Medical Center in New Orleans, La.
In fact, a study published in the Archives of Internal Medicine in January 2003 found that women who clocked an average of five hours or less of sleep a night were 39 percent more likely to develop heart disease than women who got eight hours.
Moreover, Lavie added that burning the midnight oil could also be linked with other unhealthy habits.
"Certainly, lack of sleep would have other adverse effects [both] directly and indirectly -- while not sleeping, is one munching on fatty, sugary foods, drinking alcohol, smoking, inhaling secondhand smoke in bars?" Lavie said. "[And] being tired would have adverse effects on many aspects of psychological stress ... a significant [heart] risk factor and one that adversely affects recovery from [cardiovascular] diseases."
However, some experts questioned whether simply turning in after midnight -- even if you clock at least seven hours of sleep -- really affects one's heart risk as much as this study finds.