eBAC — Estimated Blood Alcohol Concentration

Part of Statistical Methods — MORIE’s statistical-methods reference.

eBAC is a continuous outcome derived from self-reported alcohol consumption data in CPADS. MORIE computes two eBAC variants.

Widmark formula

The standard Widmark (1932) formula estimates BAC from consumed alcohol:

\[\text{BAC} = \frac{A}{r \cdot W} - \beta \cdot t\]

where

  • \(A\) = grams of alcohol consumed

  • \(r\) = Widmark distribution factor (0.68 for males, 0.55 for females)

  • \(W\) = body weight (kg)

  • \(\beta\) = elimination rate (≈ 0.15 g/dL/hr)

  • \(t\) = hours since drinking began

MORIE variants

ebac_tot

Total eBAC from the full CPADS drinking episode as reported.

ebac_legal

Binary indicator: \(\mathbb{1}[\text{eBAC} \geq 0.08\text{ g/dL}]\) (Canadian legal driving limit).

Both are available as canonical CPADS variables and participate in the CPADS_REQUIRED_VARIABLES contract.

Python API

from morie import calculate_ebac, is_over_legal_limit

ebac = calculate_ebac(drinks=5, weight_kg=70, gender="male", hours=2.0)
over = is_over_legal_limit(ebac)

eBAC-IPW module

The ebac-selection-adjustment-ipw module uses eBAC strata as a selection-correction mechanism. See Causal Inference for the statistical framework.

References

  • Widmark EMP (1932). Die theoretischen Grundlagen und die praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung. Urban & Schwarzenberg.

  • Brick J (2006). Standardization of alcohol calculations in research. Alcoholism: Clinical and Experimental Research, 30(8):1276–1287. https://doi.org/10.1111/j.1530-0277.2006.00155.x