Toward practical causal epidemiology

Abstract

Population attributable fraction (PAF), probability of causation, burden of disease, and related quantities derived from relative risk ratios are widely used in applied epidemiology and health risk analysis to quantify the extent to which reducing or eliminating exposures would reduce disease risks. This causal interpretation conflates association with causation. It has sometimes led to demonstrably mistaken predictions and ineffective risk management recommendations. Causal artificial intelligence (CAI) methods developed at the intersection of many scientific disciplines over the past century instead use quantitative high-level descriptions of networks of causal mechanisms (typically represented by conditional probability tables or structural equations) to predict the effects caused by interventions. We summarize these developments and discuss how CAI methods can be applied to realistically imperfect data and knowledge - e.g., with unobserved (latent) variables, missing data, measurement errors, interindividual heterogeneity in exposure-response functions, and model uncertainty. We recommend that CAI methods can help to improve the conceptual foundations and practical value of epidemiological calculations by replacing association-based attributions of risk to exposures or other risk factors with causal predictions of the changes in health effects caused by interventions.

Keywords: Causal artificial intelligence; Causality; Population attributable fraction; Probability of causation; Risk analysis; Statistical methods.

Fig. 1

A Bayesian network (BN) structure for air pollutants (pm2.5 = fine particulate matter, pm10 = coarse particulate matter, o3 = ozone, so2 = sulfur dioxide, no2 = nitrogen dioxide, co = carbon monoxide); cardiovascular-pulmonary disease mortality for people over age 60 (CVD60); and related weather and geographic variables (e.g., wd = wind direction, t2m = 2 m temperature, ws = wind speed, etc.). Source: [64].

Fig. 2

Seeing vs. doing. How y values of the individual data points would change if their x values were reduced by a stated amount cannot be determined from the data. Source:https://en.wikipedia.org/wiki/Simpson%27s_paradox