Risk Factor Assessment
How we weigh the risks to your health
Overview
The risk factor (R) measures the burden of habits and conditions that pull your health down over time. It runs from 0 (no risk) to 1 (the highest burden we score).
In your lifetime health curve, R sets how quickly the curve bends down:
\[ \text{score}(\text{age}) = -\alpha R \cdot \text{age}^2 + \beta H \cdot \text{age} + \gamma C \]
More risk means an earlier peak and a faster decline.
Updated October 2026 for scoring model v0.2.0. An earlier version of this post described v0.1.0.
Behavioral risks
Each behavioral risk is scored from 0 to 1, then weighted by how much that risk contributes to the burden of disease at your age, from the WHO Global Burden of Disease rankings.
| Risk | How it is scored |
|---|---|
| Smoking | Days a week × packs a day, as a share of 21 (7 days × 3 packs). |
| Alcohol | Drinks a week, as a share of the NIAAA heavy-drinking level: 8 for women, 15 for men. |
| Recreational drugs | Uses a week, as a share of 35. |
| Body mass index | A U-shaped curve (below). |
| Physical inactivity | The inverse of your physical activity score. |
| Diet | The inverse of your nutrition score. |
Each is capped at 1. For the top answers (“more than 5 a day”), we count 6.
If you have stopped: smoking, drinking or drug use you have quit counts as your past level divided by the months since you stopped. Risk fades as time passes.
Body mass index
| BMI | Risk |
|---|---|
| Under 18.5 | Rises from 0 to 1 as BMI falls to 12.5 |
| 18.5 to 25 | 0 |
| 25 to 30 | 0.2 to 0.4 |
| 30 to 35 | 0.5 to 0.7 |
| 35 to 40 | 0.7 to 0.9 |
| 40 and over | 1.0 |
A BMI of 25 to 27 scores 0 if you exercise at least 4 days a week, an hour or more a session: at that level, extra weight is likely muscle.
Conditions and family history
Conditions you report, such as hypertension, high cholesterol or diabetes, add risk through the same age-banded Global Burden of Disease figures. A condition in your family history counts at half weight. A family history of stroke also counts as a family history of high blood pressure.
The total
\[ R = \min\left(1,\; \frac{\text{behavioral risks} + \text{condition risks}}{3}\right) \]
Limitations
- Self-report: answers may understate risky behavior.
- Unmeasured factors: the survey can’t capture every risk, such as air pollution or occupational exposure.
- Validation: the model was calibrated on test surveys. It has not yet been validated against clinical outcomes; we plan to do that as real scores accumulate.
Open source
The scoring code is open source under the MIT licence: github.com/preacterik/preact-health-scoring.
References
- GBD 2019 Risk Factors Collaborators. Global burden of 87 risk factors in 204 countries and territories. The Lancet (2020).
- National Institute on Alcohol Abuse and Alcoholism. Drinking levels defined.
- World Health Organization. Body mass index classification.