Daytime napping for 30 minutes or longer is associated with an increased likelihood of developing atrial fibrillation (AF), according to research presented at European Society of Cardiology (ESC) Preventive Cardiology 2023, a scientific congress of the ESC.
“Our study indicates that snoozes during the day should be limited to less than 30 minutes,” said study author Jesus Diaz-Gutierrez (Juan Ramon Jimenez University Hospital, Huelva, Spain). “People with disturbed night-time sleep should avoid relying on napping to make up the shortfall.”
AF is the most common heart rhythm disorder, affecting more than 40 million people worldwide. People with this arrhythmia have a five times greater risk of stroke than their peers. Diaz-Gutierrez said: “Previous studies have suggested that sleep patterns may play a role in the development of atrial fibrillation, but as far as we know this was the first study to analyse the relationship between daytime napping and risk of the arrhythmia.”
The study used data from the University of Navarra Follow-up (SUN) Project, a prospective cohort of Spanish university graduates. A total of 20,348 participants free of AF at baseline completed a questionnaire every two years. Information was obtained on sociodemographic factors (age, sex, working hours), medical conditions (high cholesterol, high blood pressure, diabetes, sleep apnoea, cardiovascular diseases including AF), lifestyle (napping, smoking, exercise, coffee intake, binge drinking, adherence to a Mediterranean diet, TV watching), height and weight.
Participants were divided into three groups according to their average daily napping duration at baseline: none, less than 30 minutes, and 30 minutes or more. Short daytime nappers were defined as those who snoozed for less than 30 minutes.
New AF diagnoses were initially self-reported and subsequently confirmed by an expert committee of cardiologists, who used a predefined protocol which included reviewing medical records. The risk of AF according to daytime napping duration was analysed after adjusting for the information collected in the questionnaire.
The average age of participants at baseline was 38 years and 61% were women. During a median follow up of 13.8 years, 131 participants developed AF. Compared to short daytime nappers, those who snoozed for 30 minutes or more per day had a nearly doubled risk of developing AF(hazard ratio [HR] 1.90; 95% confidence interval [CI] 1.26–2.86). Meanwhile, compared with short nappers, risk was not elevated in those who avoided napping (HR 1.26; 95% CI 0.82–1.93).
The researchers conducted a second analysis to identify the nap duration associated with the lowest risk of atrial fibrillation. This analysis included those who reported regular napping and excluded participants who did not nap. Participants were divided into three categories according to their average daily napping duration at baseline: less than 15 minutes, 15 to 30 minutes, and more than 30 minutes. Compared with those who napped for more than 30 minutes per day, those who napped for less than 15 minutes had a 42% lower risk of developing AF(HR 0.58; 95% CI 0.35–0.95) while those who napped for 15 to 30 minutes had a 56% reduced risk (HR 0.44; 95% CI 0.27–0.72).
Diaz-Gutierrez said: “The results suggest that the optimal napping duration is 15 to 30 minutes. Larger studies are needed to determine whether a short nap is preferable to not napping at all. There are numerous potential explanations for the associations between napping and health. For example, long daytime naps may disrupt the body’s internal clock (circadian rhythm), leading to shorter night-time sleep, more nocturnal awakening and reduced physical activity. In contrast, short daytime napping may improve circadian rhythm, lower blood pressure levels and reduce stress.”