Case Study: Asymptomatic Nocturnal Bradycardia in a Healthy Adult Following Lifestyle Modifications

Case at a Glance

A 33-year-old female, with no significant past medical history, presented for evaluation after her smartwatch recorded multiple episodes of nocturnal bradycardia with heart rates as low as 38 bpm. These findings occurred in the context of recent intentional weight loss, dietary changes, and increased physical activity.

Patient's Story

The patient is a 33-year-old female who sought medical advice due to concerns raised by her wearable fitness tracker. She reported waking up to find 13 notifications from her device indicating her heart rate had dropped to a low of 38-39 bpm and remained at that level for approximately two hours during sleep. She was completely asymptomatic upon waking and throughout the night. She did note experiencing a mild episode of food poisoning the previous evening after consuming chicken, but was otherwise well. Her only regular supplements include magnesium glycinate and an over-the-counter antihistamine before bed; she also took a 1mg melatonin supplement on the night in question.

Initial Assessment

The patient presented as a healthy, well-appearing female. She had no known cardiac conditions and was not on any prescription medications. She noted that over the preceding six weeks, her average resting heart rate, as tracked by her device, had gradually decreased from 61 bpm to 50 bpm. This trend coincided with recent lifestyle changes she had implemented after a routine blood test two months prior showed borderline high cholesterol. She had successfully lost 15 pounds by adopting a diet low in sugar, sodium, and saturated fats, and increasing her physical activity, which included daily dog walks and regular treadmill use. Despite her device categorizing her cardiovascular fitness as 'above average,' she did not consider herself an athlete.

The Diagnostic Journey

The primary clinical question was to differentiate between physiological bradycardia and a potential underlying pathology. The patient's asymptomatic status was a key reassuring factor. The gradual decrease in her resting heart rate correlated directly with her improved lifestyle, weight loss, and increased exercise, suggesting a physiological adaptation and increased vagal tone. The acute episode of more significant nocturnal bradycardia was temporally associated with a bout of gastroenteritis (food poisoning), which can cause a transient increase in vagal response and further lower the heart rate. A baseline in-office EKG was recommended to rule out any underlying conduction abnormalities. Basic blood work, including a thyroid panel (TSH) and electrolyte levels, was also considered to exclude other metabolic causes. The patient's wearable device data, while not diagnostic, was acknowledged as a useful trend indicator.

Final Diagnosis

Asymptomatic Sinus Bradycardia, likely physiological and secondary to improved cardiovascular conditioning. The pronounced nocturnal episode was likely exacerbated by a transient increase in vagal tone due to a concurrent mild gastrointestinal illness.

Treatment Plan

The core of the treatment plan was patient education and reassurance. It was explained that a lower resting heart rate, especially during sleep, is a common and positive finding in individuals who improve their cardiovascular fitness. She was advised that device-generated data should be viewed as a wellness tool, not a diagnostic one, and that clinical decisions are based on symptoms and formal medical testing. She was counseled to continue her healthy lifestyle modifications. No medical or pharmacological intervention was indicated. The patient was instructed on red flag symptoms that would warrant immediate medical attention, such as dizziness, lightheadedness, syncope (fainting), shortness of breath, or chest pain.

Outcome and Follow-up

The patient was significantly reassured by the consultation. She agreed to proceed with a baseline EKG and routine follow-up blood work at her next scheduled appointment to monitor her cholesterol. She understood the benign nature of her asymptomatic bradycardia and felt confident in distinguishing between concerning symptoms and benign data from her wearable device. She planned to continue her fitness and diet regimen and follow up as needed if any new symptoms were to arise.