Is anything more pleasant than drifting off to sleep in a hammock, lawn chair, or couch with a cuddly pet and an unfinished book on a peaceful afternoon? Unfortunately, a significant new study found that frequent, regular naps are associated with health conditions such as an increased risk of hypertension and stroke, so giving in to this simple pleasure too frequently may be a warning flag.
A study of 358,451 anonymous UK Biobank records discovered the link between naps and such illnesses, which suggests it might be more than a coincidence. Since this was a correlational study, the results don’t necessarily prove that naps are to blame. However, it is certainly likely that poor sleep is the issue, and those brief periods of daytime rest may not be sufficient to shield us from the resulting health problems.
“These results are especially interesting since millions of people might enjoy a regular or even daily nap,” commented anesthesiologist E Wang of China’s Xiangya Hospital Central South University.
Earlier studies have suggested an association between daytime naps and hypertension and, consequently, one of its major complications, stroke. Taking a siesta on a single day can increase your chances of developing hypertension and stroke. Both of these conditions are severe: a stroke can result in serious, long-term disability and mortality, and hypertension, identified by persistently high blood pressure, is a leading cause of early death.
To build on earlier research, the scientists used the Biobank to carry out a study that involved Mendelian randomization, which examines how genetic differences affect an outcome to establish causality and long-term observations.
Over 500,000 UK residents between the ages of 40 and 69 who regularly submitted samples and updates on their health are included in the database during the years 2006 and 2010. In addition, some Biobank participants also participated in a daytime napping survey conducted four times between 2010 and 2019.
The researchers eliminated any participants from the Biobank data who had already experienced high blood pressure or a stroke before the trial began. This left 358,451 individuals whose health data was used in the study, including 4,333 cases of stroke and 50,507 cases of hypertension.
This large sample produced some interesting results. For example, most frequent nappers were men who smoked, consumed alcohol regularly, had lower education and income levels, and reported both snoring and insomnia.
The frequency of naps was also strongly correlated with a genetic propensity to hypertension. Regular nappers had a 24% higher risk of stroke and a 12% higher risk of hypertension than rarely and never nappers. Additionally, this risk was higher for people under 60, whose risk of hypertension was 20% as opposed to 10% for those over 60.
About 25% of the participants reported increasing their frequency of naps. The survey found that going from never to occasionally in terms of napping frequency increased the risk of hypertension by 40%. Naps and hypertension could both be signs of the same underlying issue as opposed to one causing the other.
Michael Grandner, a sleep expert and clinical psychologist at the University of Arizona, who was not involved in the study, explained:
“Although taking a nap is not harmful, many people who take naps may do so because of poor sleep at night. Poor sleep at night is associated with poorer health, and naps are not enough to make up for that. This study echoes other findings that generally show that taking more naps reflects an increased risk for problems with heart health and other issues.”
However, a causal connection should not be ruled out. Researchers have found that blood pressure can rise after a nap, which may contribute to the increased risk of stroke among daytime nappers, although a different mechanism may also be at play. In any case, it appears that additional investigation is necessary.
The researchers concluded:
“Our study, along with previous clinical studies, suggests that further examination of the mechanistic basis of the association between a healthy sleep pattern, including daytime napping, and cardiovascular disease is necessary.”
A paper detailing the research was published in Hypertension on July 25, 2022.
