A good power nap may revive many during a long workday, but nappers beware if that sojourn lasts a bit long and if you take a daily snooze.
A new study published recently has revealed that people who nap regularly during the day have a higher propensity to develop high blood pressure and strokes.
The study, published in July 2022 in Hypertension, the American Heart Association (AHA) journal, found that if the person was between 40 and 69 years old, napping frequently raised the risk of developing high blood pressure by 20 percent compared with people who never or rarely nap.
The study observed 358,451 participants in the United Kingdom who did not have a history of diagnosed sleep disorders, hypertension, or stroke. The AHA recently added sleep duration as one of its eight essential metrics to optimal heart and brain health.
The study begs the question about health in societies, like Mexico and Spain, where napping daily or taking a siesta is still a tradition. The answers to these queries are complex.
Judite Blanc, research assistant professor in the Department of Psychiatry and Behavioral Sciences and the Center for Translational Sleep and Circadian Sciences (TSCS) at the University of Miami Miller School of Medicine, shares some insights into the recent findings.
This study says that people who nap during the day are more vulnerable to high blood pressure and strokes. What do you say to this?
The relationship between daytime napping frequency with hypertension and stroke is controversial. Prior to this UK study published in the journal Hypertension in July 2022, the scientific literature demonstrated conflicting findings regarding the impact of daytime napping on high blood pressure. For instance, it remains a popular practice in South America, the Middle East, and East Asia. As a matter of fact, two previous Chinese cohort studies revealed that daytime napping could protect against hypertension while other studies found no link between daytime napping and hypertension. This new English study is important given its sample size (358,451 participants) and prospective nature (data collected for 11.16 years) linking frequency of daytime napping to essential hypertension and ischemic stroke among European individuals between aged 40 to 69 years old.
We have been taught that taking power naps was good for us. Does this study debunk that?
The term “power nap” has been introduced to emphasize its positive effect on some cognitive functions. This new UK study is only showing that napping frequently during the day may put a middle-aged person at risk for hypertension and stroke. What matters here is the frequency. Like all factors impacting health, it is the chronic exposure and the age range of individuals that are crucial. It is worth noting that as you age, you get poorer sleep at night.
Do you think the length of the nap has any bearing on this?
Absolutely. A review published in 2020 found a positive effect between short-term daytime sleep of various duration and memory consolidation. Short-term daytime sleep for up to 30 minutes between 1 p.m. and 3 p.m. can be recommended to improve the effectiveness of the intellectual work. Nevertheless, in the case of individuals with insomnia, it is recommended that they refrain from daytime napping to avoid any impact of their ability to fall asleep at night.
Going to bed tired makes it easier to fall asleep. When you take the habit of sleeping for hours during the day, this may impact your biological clocks. In the case of the new UK study, the major limitation is the fact that frequency of daytime napping was assessed with a single question: “Do you have a nap during the day? Respondents had to choose between four standardized responses: never/rarely, sometimes, usually, or prefer not to answer. Sleep wake-activity was not measured objectively with any medically approved devices such as actigraphy [a type of wearable sleep test that tracks your movements to analyze when you are asleep and when you are awake]. We have evidence showing that there is always a discrepancy between self-reported sleep habits and objective sleep data.
If indeed people who nap during the day may have sleep apnea, what are the health risks of sleep apnea?
I don’t think this study has any focus on sleep apnea, although this condition may cause daytime sleepiness. As a matter of fact, the researchers excluded persons with sleep disorders at baseline, as well as night-shift workers.
What is sleep apnea and why is it on the rise in the United States?
According to the American Academy of Sleep Medicine, an estimated 30 million U.S. adults have obstructive sleep apnea (OSA), a sleep disorder that causes breathing disruptions during sleep. And about 23.5 million of those cases are undiagnosed.
With OSA the airway is often repeatedly or partially blocked, limiting the amount of air that reaches the lungs. When this happens, patients may snore or make choking noises. The brain and body experience severe decreases in oxygen flow, causing multiple arousals from sleep during the night, or in more severe cases, several hundred times a night. Individuals may be completely unaware of experiencing these episodes while sleeping. Snoring is just one of the symptoms.
When it comes to diagnosis of OSA, there are five alarming symptoms to pay attention to: heavy snoring, choking or gasping during sleep, fatigue or daytime sleepiness, obesity, and high blood pressure. Other common symptoms of OSA include unrefreshing sleep, insomnia, morning headaches, nocturia, difficulty concentrating, memory loss, decreased sexual desire, irritability, or difficulty staying awake while watching TV or driving.
Regarding the distribution of OSA by race/ethnicity in the U.S., a study reviewed by the Center for Translational Sleep and Circadian Sciences’ (TSCS) faculty at the Miller School of Medicine, indicates that all racial/ethnic groups are affected, and some groups are at disproportionate risk.
In a population-based study of American adults aged 40 to 60 years, OSA was more prevalent among minority groups (16.3 percent) compared with whites (4.9 percent). Among Black communities, the risk for OSA has ranged from a two- to three-fold risk compared to non-Hispanic whites.
In terms of potential increase in OSA rates, the overall population prevalence ranged from 9 percent to 38 percent, and I believe this could be explained by several factors:
- Advance in diagnostic tools and better awareness around the topic among stakeholders (which is a great deal of the TSCS mission in South Florida)
- An aging population
- A worldwide epidemic of obesity, which is a major risk factor for OSA
- Environmental exposure
