We’ve all heard the same advice from doctors, coaches, and health trackers: Don’t drink coffee too late; Get seven to eight hours of sleep; A low resting heart rate (RHR) is a sign of good health.
But the question remains: how much of that is actually true for me?
Medical research gives us population truths, patterns validated across hundreds or thousands of people in controlled studies. What it often cannot show without deeper, individualized testing is whether those same cause-and-effect dynamics express themselves within your own body, under your unique conditions.
Trillies+ uses its Personal Causal Intelligence engine to explore how established medical relationships manifest uniquely in each individual, using lifestyle and physiological data from wearables and self-reports.
In this example, 30 days of real wearable and lifestyle data from one Trillies+ user were analyzed by the engine. With the user’s explicit consent, the anonymized findings are shared here to illustrate how these physiological pathways appeared in daily life.
The analysis surfaced several relationships already well described in medical literature. What stood out was seeing evidence that those same dynamics were active in this person’s daily physiology.
| Key Causal Finding | Driver (Metric) | Target (Outcome) | Effect Size | Observation |
| Quality beats Quantity | Sleep Efficiency (Drop) | Fatigue Score (Rise) | -0.63 | Efficiency, not duration, drives recovery. |
| Anticipation | HRV Mean Night (Drop) | Stress Score (Rise) | -0.56 (Lag -1) | The body sensed stress before the person did. |
| RHR Inversion | Resting Heart Rate (Drop) | Acute Stress Risk (Rise) | -0.48 | Lower isn't always better: RHR signaled strain, not recovery. |
| Chronic Ripple | Late Caffeine Event | Chronic Stress Risk (Rise) | +0.72 (Composite) | A single habit cascaded into a long-term stress load. |
| Body's Whisper | Respiration Rate (Rise) | Bad Sleep Transitions (Rise) | +0.38 | Subtle breathing changes fragmented restorative sleep. |
Sleep Efficiency - Quality beats Quantity
We’re often told that simply getting more sleep is better. For this user, the data showed something more precise: how efficiently you sleep matters far more than how long.
When sleep efficiency dropped (the percentage of time asleep versus time in bed), fatigue and stress rose the next day, even if total sleep hours stayed the same. Reduced efficiency predicted next-day physiological and emotional strain.
This relationship reflected a causal pattern consistent with clinical findings, observed directly in this individual’s data. In this case, efficiency, not duration, was the functional driver of recovery.
HRV - The Heart That Knows Before You Do
Heart Rate Variability (HRV) measures how flexibly the nervous system switches between action and recovery. Clinicians recognize that low HRV reflects stress, but in this user’s data, HRV didn’t just move with stress; it predicted it.
The results showed a one-day lag: HRV dropped the night before fatigue and stress levels rose. The parasympathetic nervous system was sending an early warning of strain before the user was consciously aware of it.
Trillies+ mapped that relationship as a potential causal sequence: lower HRV → higher next-day stress.
Resting Heart Rate - When "Lower" Backfires
A low resting heart rate is widely regarded as a marker of good fitness. For this user, that rule flipped. A drop in RHR coincided with higher acute-stress indicators and greater fatigue, suggesting temporary autonomic suppression - the nervous system’s adaptive response to accumulated strain or overtraining rather than genuine recovery.
That lower-than-normal RHR was not a sign of peak health; it reflected a body under acute strain, momentarily overcompensating.
This inversion, “lower isn’t always better,” mirrors what sports scientists monitor when predicting overtraining or early signs of illness.
Caffeine - The Ripple That Reaches Risk
Most people know caffeine can disturb sleep. What the analysis uncovered was how that single habit rippled through multiple physiological stages, extending all the way to elevated long-term stress risk. The chain was clear:
Late caffeine intake → lower sleep efficiency → higher morning fatigue → elevated daily and chronic stress risk.
Identifying such multi-stage causal patterns illustrates the intent of Personal Causal Intelligence: connecting daily habits with physiological outcomes. A simple, everyday behavior quietly shifted the body’s stress baseline over time.
From Population Science to Personal Causality
We weren’t surprised that the engine rediscovered relationships consistent with existing medical understanding. What’s meaningful is that, for the first time, we can observe how those same mechanisms appear within an individual’s own data.
Medicine explains both the what and the why of human health. Trillies+ personalizes that understanding by showing how those same physiological mechanisms operate within your own context and data.
This marks a shift from population-level understanding to individual causal illustration. When advice like “avoid caffeine before bed” aligns with your own data, it becomes personal evidence.
Closing Reflection
We rely on medical science to uncover the principles that govern human health. Personal Causal Intelligence builds on that foundation by showing how those same principles express themselves in each individual's data.
The goal is not to replace or challenge medical expertise, but to complement it with a data-driven view of how established wisdom functions in everyday life.
When medical advice becomes personal truth, health knowledge evolves into personal intelligence.
*The content of this article is for informational purposes only and does not constitute medical advice. It is not intended to diagnose, treat, cure, or prevent any condition, nor to replace consultation with a qualified healthcare professional. All data discussed are anonymized, used with the user's explicit consent, and analyzed for research and educational illustration only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
About the Author
Darren S. is the founder of Trillie Inc., bringing over 20 years of experience in technology and product management. He is passionate about advancing causal AI and building sustainable solutions that make practical, affordable technology accessible to people and communities everywhere. Connect on LinkedIn