Long Daytime Naps and Short Nighttime Sleep Linked to Triple the Risk of Atrial Fibrillation: Insights from a Spanish Cohort Study

Highlight

• Individuals taking long daytime naps (≥30 minutes) had a 62% increased risk of developing atrial fibrillation (AF) compared to those with short naps (<30 minutes).
• Inadequate nighttime sleep (<6 or >8 hours) was associated with an 89% higher risk of incident AF.
• Participants with both long naps and inadequate nighttime sleep exhibited a threefold increase in AF risk compared to those with optimal sleep habits.
• Sleep patterns may be a modifiable risk factor for AF, highlighting potential avenues for prevention.

Background

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia worldwide, affecting approximately 33 million people globally. It is a major contributor to stroke, heart failure, and increased mortality, and its prevalence is rising due to aging populations and the increasing burden of cardiovascular risk factors. While traditional risk factors for AF, such as hypertension, obesity, and diabetes, are well established, there is growing interest in the role of modifiable lifestyle factors, including sleep patterns, in AF pathogenesis. Sleep disturbances and abnormal sleep duration have been linked to various cardiovascular outcomes, but robust prospective data specifically relating daytime napping and nighttime sleep duration to incident AF remain limited.

Study Overview and Methodological Design

This prospective cohort study, led by Jesús Díaz-Gutiérrez and colleagues at the University Hospital Juan Ramon Jiménez, enrolled 20,827 Spanish university graduates free from AF at baseline. Participants, predominantly young to middle-aged adults (mean age 36.0–39.7 years; 57.4%–65.2% women), completed validated questionnaires regarding their sleep habits, including daytime napping and nighttime sleep duration.

Daytime napping was categorized as:

• No nap
• Short nap (<30 minutes per day)
• Long nap (≥30 minutes per day)

Nighttime sleep duration was classified as:

• Adequate (6–8 hours per night)
• Inadequate (<6 hours or >8 hours per night)

Participants were followed for a median of 15.1 years. Incident cases of AF were ascertained through physician diagnosis, medical records, and confirmation using standard criteria. Multivariable Cox proportional hazards models adjusted for demographic, lifestyle, and clinical covariates were used to estimate the association between sleep patterns and AF risk.

Key Findings

During the 15-year follow-up, 163 incident cases of AF were documented. The major findings include:

• Long daytime naps (≥30 min/day): Associated with a 62% higher risk of incident AF compared to short naps (<30 min/day); adjusted hazard ratio (aHR) 1.62, 95% CI 1.10–2.39.
• Inadequate nighttime sleep: Linked to an 89% increased risk for AF compared with adequate sleep duration; aHR 1.89, 95% CI 1.10–3.23.
• Combined long nap and inadequate nighttime sleep: Participants with both risk factors had a threefold higher risk for AF (aHR 3.19, 95% CI 1.30–7.79) compared to those with no or short naps and adequate nighttime sleep.
• No significant association was observed between not napping and incident AF risk.

These results remained robust after adjusting for a range of potential confounders, including age, sex, body mass index, smoking, alcohol intake, physical activity, and comorbidities.

Mechanistic Insights and Pathophysiological Context

The biological mechanisms linking sleep patterns to AF risk are multifactorial. Inadequate nighttime sleep may promote sympathetic nervous system activation, systemic inflammation, and changes in autonomic balance, all of which facilitate atrial remodeling and increase arrhythmogenic potential. Long daytime naps may be a compensatory response to poor nighttime sleep, but could also disrupt circadian rhythms, further impairing cardiovascular homeostasis. Sleep fragmentation and sleep deprivation are known to increase neurohormonal stress, blood pressure variability, and pro-inflammatory cytokine release, all implicated in the pathogenesis of AF. Additionally, abnormal sleep patterns can contribute to metabolic dysfunction and exacerbate comorbidities such as hypertension and obesity, key drivers of AF risk.

Clinical Implications

These findings have important implications for both clinicians and public health practitioners. Sleep patterns—and specifically the combination of extended daytime napping with inadequate nighttime sleep—represent potentially modifiable risk factors for AF. Clinicians should consider incorporating sleep assessment into cardiovascular risk profiling, especially in younger adults and those with emerging or established risk factors for AF. Patient counseling on optimal sleep hygiene may offer a simple, cost-effective strategy to reduce AF incidence and its associated complications. Given the high lifetime risk and substantial morbidity linked to AF, even modest reductions in risk factors could yield significant population health benefits.

Case Vignette: A 38-year-old woman presents for an annual checkup. She reports daytime fatigue, routinely takes 1-hour naps, and typically sleeps only 5 hours per night due to work stress. Her cardiovascular risk profile is otherwise unremarkable. Based on these new findings, her clinician discusses the potential link between her sleep habits and future AF risk, recommending behavioral strategies to improve nighttime sleep duration and reduce nap length.

Limitations and Controversies

Several limitations warrant consideration. The study population consisted of Spanish university graduates, which may limit generalizability to older or more diverse populations. Sleep patterns were self-reported, introducing potential misclassification or recall bias. Although extensive adjustment for confounders was performed, residual confounding cannot be excluded. The temporal relationship between changes in sleep patterns and AF onset was not explored, and the mechanisms underlying these associations remain speculative. Furthermore, the study did not assess sleep disorders such as obstructive sleep apnea, a known risk factor for AF, which could mediate some of the observed associations.

Controversially, some previous studies have reported protective effects of short, regular naps on cardiovascular health, raising questions about the optimal balance between daytime rest and nighttime sleep. More research is needed to disentangle these complex relationships.

Expert Commentary or Guideline Positioning

Current major guidelines from the American Heart Association and European Society of Cardiology emphasize traditional risk factor modification for AF prevention but do not specifically address sleep duration or naps. However, growing evidence—including this large prospective study—suggests sleep patterns merit greater attention in AF risk assessment and preventive strategies. As the authors note, “[The study] findings might have important clinical and public health implications, as sleep patterns could be a modifiable risk factor for AF.”

Conclusion

This prospective cohort analysis provides compelling evidence that both long daytime naps and inadequate nighttime sleep, particularly in combination, are associated with a substantially increased risk of developing atrial fibrillation. These modifiable behaviors represent promising targets for prevention efforts. Future research should explore causality, underlying mechanisms, and the impact of interventions aimed at optimizing sleep habits on AF incidence.

References

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6. Díaz-Gutiérrez J, Goni L, Martínez-González MÁ, Barón-Esquivias G, Bazal P, de la Fuente-Arrillaga C, Barrio-López MT, Bes-Rastrollo M, Ruiz-Canela M. Sleeping and the risk of atrial fibrillation: a prospective study in the SUN cohort. Eur J Prev Cardiol. 2025 Jul 24:zwaf377. doi: 10.1093/eurjpc/zwaf377