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.
In other words, perhaps the life of a night owl involves more unhealthy habits than those who follow Franklin's advice on "early to bed, early to rise," in which case, it is the unhealthy late-night habits -- rather than the late bedtime -- that raise one's heart risk.
"For example, for many years we thought drinking coffee was linked to heart disease, so there was some advice to patients not to drink as much coffee, but we found over time that people who drank more coffee were also more likely to smoke and have other unhealthy habits, so that was actually causing the heart risk," said Dr. Daniel Jones, past president of the American Heart Association and vice chancellor for health affairs and dean of the University of Mississippi School of Medicine.
For this reason, Jones said it would be premature for doctors to make recommendations to patients about altering their bedtimes rather than their sleep duration, which has been shown to affect cardiovascular health in multiple studies.
"The author of the study encourages people to go to bed earlier, but I think most scientists will look at this and say it's premature advice," Jones said.
However, Jones explained that although the study does not prove a late bedtime causes the heart risk, this finding may still make biological sense.
"There are a lot of potential reasons for this causal link, [such as] some of the chemicals or hormones in our body that are tied to sleep," Jones said. "People with less deep sleep and less duration of sleep have more adrenaline release, and it's likely that some of those hormones or chemicals could be related to the poor health of those with less healthy sleep habits."
According to Dr. Virend Somers, consultant in cardiovascular diseases and professor of medicine at the Mayo Clinic in Rochester, Minn., another possible explanation for the link between later bedtimes and cardiovascular risk could be that people who hit the hay after midnight actually clock less sleep than they think.
"Maybe when you go to sleep after midnight your sleep duration is shorter than you think it is," Somers said. "In other words, if I went to sleep at midnight and got up at 8 a.m., but my wife and kids got up at 6 a.m. to go to school, I might think that I slept a full eight hours, but I actually woke up several times when the house was noisy at 6 a.m."
Whatever the explanation may be, it remains well-established that a good night's sleep is an extremely important factor in leading an overall healthy lifestyle.
"People who sleep less seem to have poorer health in general and people who sleep more tend to have better health in general and that includes heart disease," Jones said.