Background: Adults with allergic rhinitis experience elevated resting heart rates and altered heart rate variability in comparison to healthy peers. However, no information is available on acute, daily changing factors that could underlie these cardiac alterations.

Aim: To estimate associations between daily heart rate characteristics (i.e. resting heart rate, autocorrelation and sample entropy) and allergy symptom severity and mood in adults with allergic rhinitis.

Methods: Adults with a tree pollen allergy (n=82) self-reported daily symptom severity (score: 0-44) and mood (score: 0-4) in a mobile health application during two pollen seasons of hazel, alder and birch trees. Heart rate characteristics were extracted from daytime heart rate measurements (Mio Alpha 2 wristwatch; 1 Hz; >6 hours/day). Associations between heart rate characteristics and allergy symptom severity or mood (lag 0-2) were estimated using linear mixed effects regressions, adjusted for potential confounders with a random intercept for individuals.

Results: The analyses included 3800 participant-days. A one-point increase in symptom severity was associated with an increase in resting heart rate of 0.07 (0.02 to 0.13) beats per minute on the next day. A one-point improvement in mood was associated with a decrease in autocorrelation of -0.00027 (-0.00052 to -0.00001) and an increase in sample entropy of 0.0087 (0.0049 to 0.0125) on the same day.

Conclusion: Results suggest that a higher symptom burden provokes the cardiovascular system (higher resting heart rate on the next day), while a better mood might be related to a healthier, more adaptable cardiovascular system (more irregular heart rate on the same day).