Researchers in Spain have found an association between the length of a daytime nap and the risk of developing atrial fibrillation (AF). The authors note that previous research has identified a potential relationship between sleep patterns and AF – but not between AF and napping.
The finding was presented by Jesus Diaz-Gutierrez, MD, of Juan Ramon Jimenez University Hospital, Huelva, Spain at the recent annual congress of the European Association of Preventive Cardiology. In the presentation abstract, the researchers note that “daytime napping is a widespread healthy habit particularly in Mediterranean countries.” In this case, less is more.
The investigators analyzed data from 20,348 participants in the SUN project, a dynamic, prospective cohort of Spanish university graduates. Participants’ average age at baseline was 38 and 61% were women. At baseline, participants were free of AF. Their daytime napping was assessed, and they were categorized according to their average daily napping time and followed for a median of 13.8 years, with a retention proportion of 91%.
During follow-up, 131 incident cases of AF were identified. Compared to participants with short daytime napping (<30 minutes/day), those who slept ≥30 minutes/day had a significant 90% higher relative risk of incident AF (adjusted hazard ratio [HR], 1.90).
By contrast, no significant risk was observed for participants who did not nap (adjusted HR = 1.26; 95% CI: 0.82, 1.93).
After excluding participants who reported not napping, those with shorter daytime napping had a lower risk of developing AF, with the greatest risk reduction between 15-30 minutes/day (adjusted HR , 0.44) in comparison to sleeping >30 minutes/day.
Specifically, 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 atrial fibrillation (HR 0.58) while those who napped for 15 to 30 minutes had a 56% reduced risk.
The authors concluded:
- Daytime napping was significantly associated with the risk of developing AF.
- A longer nap (≥30 minutes/day) was associated with an increased risk.
- A shorter nap (between 15-30 minutes/day) was associated with a lower risk of incident AF.
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.”