Getting Too Little or Too Much Sleep Can Harm Your Health — Here’s How

Researchers say six to eight hours of sleep is the “sweet spot” for most people.

Researchers say poor sleep is a risk for health problems just like an unhealthy diet and inadequate exercise. Getty Images

Six to eight hours of sound sleep is the sweet spot for cardiovascular health. No more and especially no less.

That’s the conclusion of a new study showing that people who slept less than six hours were 27 percent more likely to have atherosclerosis throughout their body.

Women who slept more than eight hours nightly also were at increased risk of plaque buildup (or “hardening”) in the arteries.

It’s not just the amount of sleep that’s important for cardiovascular health either.

Researchers reported in the Journal of the American College of Cardiology that study subjects who reported poor quality of sleep were 34 percent more likely to have atherosclerosis than those who generally got a good night’s sleep.

Alcohol and caffeine use were higher among those who reported short or disrupted sleep, researchers also noted.

“It is almost common sense that it is better to have a few hours of good sleep than spend hours agitated by the impossibility of reaching a restful sleep,” said José M. Ordovás, PhD, a senior study author as well as a researcher at the Centro Nacional de Investigaciones Cardiovasculares Carlos III in Madrid and director of nutrition and genomics at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

The study is the first to show that objectively measured sleep is independently associated with atherosclerosis throughout the body, not just in the heart.

“It could be that at the early stages of the disease, the plaque development is happening faster in the periphery than in the heart,” Ordovás told Healthline. “The bottom line is that future studies should examine the multi-territory assessment of atherosclerosis to identify with more precision — and probably earlier — those individuals at risk.”

Seeking ‘precision sleep’

Past studies have found a link between lack of sleep and increases in risk factors for heart disease, including high blood glucose levels, high blood pressure, inflammation, and obesity.

Ordovás said his study found that short or poor sleep contributed to atherosclerosis even after controlling for other risk factors, “suggesting that additional, unmeasured mechanisms are acting to increase the risk due to lack of sleep.”

Six to eight hours of sleep “seems to be the proper amount of time to maintain the homeostasis of the circadian rhythm,” he said.

He also noted that in future research, “just like we talk about precision medicine or precision nutrition, we also want to achieve precision sleep.”

“One aspect that remains to be understood from this data is if sleep timing — when people sleep in relation to their circadian rhythm — might confer an additional associated increase in vascular disease risk,” Dr. Jeffrey Durmer, medical director of the Atlanta-based sleep health company FusionHealth, told Healthline. “From multiple lines of human and animal circadian rhythm neurobiological research, one would suspect that the timing of sleep has just as much, if not more, impact on the vasculature as a reduced duration and/or quality of sleep.”

Dr. Purvi J. Parwani, a cardiologist at the Loma Linda University International Heart Institute in California, told Healthline that research shows that levels of the stress hormone cortisol, along with steroid levels and the appetite hormone, are known to rise with excessive sleep.

Inadequate sleep, on the other hand, doesn’t allow body systems to rest and repair properly, raising the risk of arrhythmia, congestive failure, and blood pressure surges, among other consequences, she said.

How the study was done

The study looked at a group of 3,974 people in Spain participating in ongoing research to detect vascular lesions using imaging techniques.

The average age of participants was 46 and none had any history of heart disease.

To gather information on sleep patterns, each participant wore an actigraphy monitor for seven nights. The device monitors activity and movement.

Participants also underwent 3D heart ultrasound and cardiac CT scans for signs of heart disease.

The relative health of the study group, and the fact that sleep was measured by researchers and not self-reported, make the findings especially strong, said Parwani.

“We knew that sleep was important, but this study shows that it could be a risk factor for cardiovascular disease independent of others that we have found,” she said.

In an editorial accompanying the study, Dr. Daniel J. Gottlieb of the VA Boston Healthcare System as well as Brigham and Women’s Hospital division of sleep medicine at Harvard Medical School and Dr. Deepak L. Bhatt of the Brigham and Women’s Hospital division of cardiovascular medicine, called for further studies to determine whether changing sleep behaviors can improve heart health.

They said such research is “needed to place sleep with confidence alongside diet and exercise as a key pillar of a healthy lifestyle.”

“Cardiovascular disease is a major global problem and we are preventing and treating it using several approaches, including pharmaceuticals, physical activity, and diet,” said Ordovás. “But this study emphasizes we have to include sleep as one of the weapons we use to fight heart disease.”

The bottom line

Lack of sleep, disrupted sleep, and even too much sleep may increase the risk of cardiovascular disease.

Poor sleep habits seem to cause atherosclerosis throughout the body, not just the heart.

Future research could see poor sleep ranked among the main risk factors for heart and coronary artery disease alongside unhealthy diet and a lack of exercise.