Regular naps have been linked to higher risks of high blood pressure and stroke, as those who nap more often sleep worse at night
Researchers in China have found that regular naps may be a potential causal risk factor for high blood pressure and/or stroke, as sleep is an influential factor in people’s overall health.
Using Mendelian randomization, they found validation of genetic risk for determining whether frequent napping was associated with high blood pressure and ischemic stroke – finding that higher napping frequency was linked to genetic propensity to risk of high blood pressure.
E Wang, Ph.D., MD, said, “These findings are particularly exciting because millions of people could benefit from a regular or even daily nap.”
The study found that a higher percentage of habitual naps were from men
From the study, researchers found that the highest percentage of regular naps had lower levels of education and income, and reported smoking cigarettes, daily drinking, insomnia, snoring, and being a night person by compared to never or sometimes naps.
Compared to people who said they never nap, people who usually nap had a 12% higher chance of developing high blood pressure and a 24% higher chance of having a stroke.
Participants under the age of 60 who usually took a nap had a 20% higher risk of developing high blood pressure compared to people of the same age who never took a nap.
However, after the age of 60, habitual naps were associated with a 10% higher risk of high blood pressure compared to those who reported never taking a nap.
During the study, about 75% of participants stayed in the same nap category throughout the study.
Overall, using Mendelian randomization, they found that if nap frequency increased by one category – from never to sometimes or sometimes to usually – the risk of high blood pressure could increase by up to 40%.
Although taking a nap in itself is not harmful, many people who do may do so because of poor sleep at night.
Michael A. Grandner, Ph.D., MTR, said, “This may be because, although taking a nap in itself is not harmful, many people who take naps may do so because of poor sleep at night. Poor sleep at night is associated with poor health, and naps alone aren’t enough to offset that.
“This study echoes other findings that generally show that taking more naps appears to reflect an increased risk of heart health and other conditions.”
How did the team collect the nap data?
Using information from UK Biobank, which is a large biomedical database and research resource containing anonymous genetic, lifestyle and health information from half a million UK participants, they recruited more of 500,000 participants aged 40-69 who lived in the UK between 2006 and 2010.
They regularly provided blood, urine and saliva samples, as well as detailed information about their lifestyle. The daytime napping frequency survey was conducted 4 times from 2006 to 2019 in a small proportion of UK Biobank participants.
The study group excluded records of people who had ever had a stroke or had high blood pressure before the start of the study, leaving about 360,000 participants to analyze the association between napping and first reports of stroke or high blood pressure, with an average follow-up of about 11 years.
Participants were divided into groups based on self-reported napping frequency: “never/rarely”, “sometimes” or “usually”.
Using this data, they were able to extract a sample large enough for all types of sleepers, finding that those with a higher likelihood of napping had an increased risk of high blood pressure and stroke.
The results were published in the American Heart Association.