You've been tracking your heart rate variability (HRV) on your Apple Watch or fitness tracker, and the numbers seem concerningly low. Maybe your HRV dropped suddenly, or it's been consistently lower than the "healthy" ranges you've seen online. You're asking the question millions of health-conscious people ask: why is my HRV so low?

HRV is one of the most important biomarkers for longevity and recovery. In My Bio Age, HRV is a key driver of your biological age calculation—and for good reason. Research consistently shows that higher HRV correlates with better cardiovascular health, lower stress, improved recovery, and longer lifespan. Understanding why your HRV might be low is the first step to improving it.

What is HRV and why does it matter?

Heart rate variability measures the variation in time between consecutive heartbeats. Unlike heart rate (which might be a steady 60 BPM), HRV captures the subtle millisecond differences between beats. Higher variability indicates your autonomic nervous system is flexible and responsive—a sign of good health and recovery capacity.

Apple Watch measures HRV using the SDNN method (standard deviation of normal-to-normal intervals), typically during sleep or rest periods. My Bio Age ingests this data and tracks your HRV trends over 14 weeks, comparing current values to your personal baseline and age-appropriate norms.

7 common causes of low HRV

1. Poor sleep quality or insufficient sleep

Sleep is when your parasympathetic nervous system should dominate, allowing HRV to rise. If you're getting less than 7 hours, sleeping irregularly, or experiencing poor sleep quality, your HRV will suffer. Sleep disruption—from alcohol, late meals, screen time, or sleep disorders—directly suppresses HRV.

Fix: Prioritize sleep consistency. Go to bed and wake up at the same time daily. My Bio Age tracks Sleep Regularity as a separate metric because it's that important.

2. Overtraining or insufficient recovery

Hard training without adequate recovery chronically elevates stress hormones and suppresses HRV. If you're training intensely every day without rest days, your body never fully recovers. Ironically, the fittest people sometimes have the worst HRV because they overtrain.

Fix: Use My Bio Age's Recovery Capacity metric and Training Load zones to balance effort and recovery. When recovery is low, prioritize rest.

3. Chronic stress (work, life, emotional)

Your autonomic nervous system doesn't distinguish between a work deadline and a physical threat. Chronic psychological stress keeps your sympathetic ("fight or flight") system elevated, suppressing HRV. Even if you're physically healthy, unmanaged stress tanks your variability.

Fix: Incorporate stress management: meditation, breathwork, nature exposure, or whatever helps you decompress. The AI Coach in My Bio Age can help identify if stress patterns correlate with your HRV dips.

4. Alcohol consumption

Even moderate alcohol consumption significantly reduces HRV, especially during sleep. Alcohol disrupts sleep architecture and keeps your heart rate elevated throughout the night. The effect can last 2-3 days after drinking.

Fix: Reduce or eliminate alcohol, especially in the hours before bed. Track your HRV on drinking vs. non-drinking nights to see the impact.

5. Dehydration and poor nutrition

Dehydration strains your cardiovascular system, and your heart has to work harder to circulate blood. Poor nutrition—especially low electrolytes, excessive sugar, or inflammatory foods—also impacts HRV negatively.

Fix: Stay hydrated throughout the day. Eat whole foods, adequate protein, and consider tracking how different foods affect your overnight HRV.

6. Illness or fighting infection

When your immune system is active, HRV drops as your body diverts resources to fighting the infection. A sudden HRV drop can actually predict illness before symptoms appear— it's one of the earliest warning signs something is off.

Fix: If HRV drops unexpectedly, prioritize rest and watch for other symptoms. My Bio Age's weekly digest will flag unusual drops so you notice early.

7. Age and baseline differences

HRV naturally declines with age. A 50-year-old will typically have lower HRV than a 25-year-old, even if both are equally healthy. Comparing your HRV to internet averages without accounting for age leads to unnecessary concern.

Fix: Focus on your personal trend, not absolute numbers. My Bio Age compares your HRV to age-appropriate norms and tracks whether you're improving relative to your own baseline.

How to improve your HRV

Prioritize sleep consistency — Same bedtime and wake time, 7-9 hours.
Balance training and recovery — Use recovery metrics to guide effort.
Manage stress actively — Meditation, breathwork, or other practices.
Limit alcohol — Especially in the 3-4 hours before sleep.
Stay hydrated — Water and electrolytes throughout the day.
Cold exposure — Cold showers or ice baths stimulate vagal tone.
Aerobic exercise — Zone 2 training improves baseline HRV over time.

Track HRV trends with My Bio Age

My Bio Age doesn't just show you today's HRV—it tracks your 14-week trend, compares to your personal baseline, and shows how HRV impacts your biological age. The on-device AI Coach can answer questions like "Why did my HRV drop?" by analyzing correlations with sleep, activity, and recovery patterns.

Download My Bio Age to understand your HRV in context. Your biological age depends on it.