When it comes to sleep, quality may be just as important as quantity

When it comes to healthy sleep, it's not just how long a person is at rest that matters. Other factors, such as how long it takes to fall asleep, keeping a regular sleep schedule and the overall satisfaction with sleep, can all affect heart and brain health, according to a new science report.

The report summarizes the latest evidence on the relationship between multiple components of sleep and cardiometabolic health factors, such as body fat, blood sugar, cholesterol and blood pressure, as well as how healthy sleep affects physical health and mental well-being. The scientific statement from the American Heart Association was published Monday in the journal Circulation: Cardiovascular Quality and Outcomes.

"There is increasing evidence that sleep health is about more than the number of hours you sleep each night," Dr. Marie-Pierre St-Onge, chair of the statement's writing group, said in a news release. She is an associate professor of nutritional medicine in the department of medicine and director of the Center of Excellence for Sleep & Circadian Research, both at Columbia University Irving Medical Center in New York City.

"Suboptimal sleep raises the risk for cardiovascular disease, along with risk of cognitive decline, depression, obesity, as well as high blood pressure, blood sugar and cholesterol levels," she said.

The American Heart Association includes sleep duration in its eight metrics for good heart and brain health. Most adults need seven to nine hours of sleep each night. Studies show that not getting enough increases the risk of atrial fibrillation, or AFib, a type of irregular heartbeat; cardiometabolic syndrome, a group of conditions that raise the risk for Type 2 diabetes, heart disease and stroke; and blood pressure that doesn't decrease as much as it should during sleep. Getting too much sleep also has been linked to a higher risk for cardiometabolic syndrome, along with stiffened arteries, stroke or death from heart disease or stroke.

However, sleep duration is just one facet of a good night's rest. According to the report, no single component captures people's sleep experiences or how their body responds to it. Other sleep components include continuity, timing, satisfaction, regularity, sleep-related daytime functioning and sleep architecture.

Sleep continuity includes how long it takes a person to fall asleep, how often they wake during the night, how long they're awake during the night, unplanned early awakening and sleep apnea. Poor sleep continuity has been linked to a higher risk for AFib, heart attack, high blood pressure and greater insulin resistance.

There is less data on sleep timing, which refers to the time a person typically goes to sleep and whether they are sleeping during the day or night. However, some studies suggest going to sleep at midnight or later, compared to earlier, may raise the risk of overweight or obesity, insulin resistance and high blood pressure.

Lower satisfaction with one's sleep quality has been linked to higher blood pressure, stiffer arteries, coronary heart disease and blood pressure that doesn't decrease during the night.

Not having a consistent sleep pattern has been linked to a higher risk for obesity, cardiovascular disease, high blood pressure, inflammation and blood pressure that doesn't drop during the night. Greater consistency has been shown to lower the risk for cardiovascular death.

Sleep-related daytime functioning, or how alert a person feels during the day, also affects heart health. Excessive daytime sleepiness has been linked to heart disease and stroke and related deaths.

Sleep architecture – or the cycling between stages of light and deep sleep – may also play a role in heart health. Some studies suggest disruptions to sleep affect people differently based on the cycle that gets disrupted.

The statement also addresses the impact of social drivers of health – such as socioeconomic status, pollution and safety – on sleep health. More than 300 studies show consistent associations between lower socioeconomic status and suboptimal sleep health. Other research has shown people in historically underrepresented racial and ethnic groups sleep less and are more likely to experience worse sleep continuity and sleep satisfaction, later bedtimes, more irregular sleep patterns, higher daytime drowsiness and a greater number of sleep disorders.

"It's important to know that every individual has different sleep experiences, and these differences may contribute to other health inequities," St-Onge said. "Including different components of sleep in discussions with patients provides essential information that can help health care professionals improve care."

The statement concludes that advances are needed in how to measure and analyze the full range of sleep components affecting health so they can be better addressed and improved.

St-Onge said people should pay close attention to how they are sleeping just as they do other aspects of health and well-being.

"Some changes in sleep across the life course are natural," she said. "However, individuals should not accept poor or worsening sleep as a 'fact of life' or unavoidable consequence of the aging process. If they note new difficulties falling or staying asleep, or excessive daytime sleepiness, they should discuss this with their doctor for further evaluation and potential treatment."