Correlation checklist: does a daily glass of wine extend life?

Question

A wellness blog claims that people who drink one glass of wine a day live longer than non-drinkers, and urges you to drink wine for longevity.

Before believing it, list every reason wine intake and longevity could correlate without wine causing longevity.

Accepted Answer

Run the correlation-to-causation checklist. Each item is a way X (wine) and Y (longevity) can move together without X causing Y. 1. Reverse causation / sick-quitter effect. Being healthy causes moderate drinking, not the other way around. People who fall ill often stop drinking, so the "non-drinker" group is stuffed with the already-sick, making moderate drinkers look healthier by comparison. 2. Confounders (common causes). Moderate wine drinkers tend to be wealthier, better educated, more socially connected, and to exercise and eat better. All of those independently raise longevity and also …

Correlation checklist: does a daily glass of wine extend life?

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