Sinus arrhythmias are more common in which group?

• A. Older adults
• B. Middle-aged adults
• C. Younger populations
• D. Those with hypertension

Answer: (C)

Sinus arrhythmia, specifically respiratory sinus arrhythmia, is a normal, breathing-related fluctuation in heart rate driven by the autonomic nervous system. When you inhale, vagal (parasympathetic) tone diminishes and the heart rate rises; when you exhale, vagal tone increases and the heart rate falls. This variability is more pronounced in younger people because their autonomic control, especially the parasympathetic system, is more dynamic and capable of larger swings in response to breathing. As people age, autonomic regulation tends to become less reactive, so the beat-to-beat variation seen with respiration becomes subtler. Hypertension doesn’t determine this pattern; it’s primarily related to age and autonomic tone. So, sinus arrhythmias are more common in younger populations.