July 25, 2022

expert reaction to study looking at nap frequency and blood pressure

A study published in Hypertension looks at nap frequency and hypertension or ischemic stroke.

Prof Paul Leeson, Professor of Cardiovascular Medicine, University of Oxford, said:

“Having a sleep during the day has been associated with higher risk of heart problems such as high blood pressure.  However this might just be a coincidence.  There could be lots of other health reasons that explain why someone is sleeping more during the day, which also happen to explain why that person has a higher risk of heart disease.

“This study is different because it uses ‘Mendelian Randomisation’ to test whether there is a link.  For this type of study you need to identify a gene, or set of genes, that predispose someone to the thing you are interested in, in this case, a tendency to sleep during the day.  As it has been inherited, this tendency will have been present since birth, before anyone had heart disease.  If in later life those with the inherited tendency to sleep do develop high blood pressure, this suggests the tendency to sleep during the day is the initial problem.

“There are potential weaknesses in this analysis.  Sleeping during the day was classified in a very simple way in most of the studies analysed and there can be many reasons for why people decide to nap.  The length of sleep, the number of times they fall asleep and the quality of sleep can all vary.  It is not clear whether the genes just identified a particular type of daytime napping that linked with high blood pressure or whether this is a general effect.

“The other problem is that there is still no proven explanation for why there might be a link.  This makes it very difficult to know how to prevent the problem.  Simply stopping yourself having that nap might not be a solution as this could cause other problems with sleepiness and poor sleep patterns.

“So, an interesting finding, but a lot more work needed before it will be possible to understand how this knowledge could help improve care for patients.”

‘Association of Nap Frequency With Hypertension or Ischemic Stroke Supported by Prospective Cohort Data and Mendelian Randomization in Predominantly Middle-Aged European Subjects’ by Min-jing Yang et al. was published in Hypertension on Monday 25 July 2022.

DOI: 10.1161/HYPERTENSIONAHA.122.19120

https://www.ahajournals.org/doi/10.1161/HYPERTENSIONAHA.122.19120

Declared interests

Prof Paul Leeson: “No relevant conflicts to declare.”