Opens the alcohol cluster. The famous finding that moderate drinkers outlive abstainers — the
J-curve — is the textbook case of a protective lower arm that dissolves under scrutiny. Two
independent methods say the protection is largely not real.
The observational J-curve — the appearance
- All-cause mortality (Stockwell, 87 studies). Unadjusted, the «classic J-shaped curve» appears: low-volume drinkers (1.3-24.9 g/day) «RR = 0.86, 95% CI [0.83, 0.90]» vs abstainers; occasional drinkers «0.84 [0.79, 0.89]»; former drinkers elevated «1.22 [1.14, 1.31]». [EXTRACTED (Stockwell - Moderate Drinkers Mortality Risk 2016) chunk 01, Table 2]
- Vascular disease (Millwood, China Kadoorie, 500k). Self-reported intake had «U-shaped associations with the incidence of ischaemic stroke… intracerebral haemorrhage… and acute myocardial infarction; men who reported drinking about 100 g of alcohol per week… had lower risks of all three diseases than non-drinkers or heavier drinkers.» [EXTRACTED (Millwood - Alcohol and Vascular Disease Genetic Evidence 2019) chunk 01, Findings]
Why the lower arm is an artifact — two independent adjudications
1. Bias-corrected observational (Stockwell). Correcting for how abstainers are defined erases the protection. The driving bias is former-drinker misclassification (sick-quitters who quit because they are ill, counted as abstainers, making the referent look unhealthy):
- fully adjusted for abstainer biases + study quality, low-volume «RR = 0.97, 95% CI [0.88, 1.07]» — no significant protection; former drinkers rise to «1.38 [1.24, 1.54]».
- the 13 bias-free studies show «no significant protection for low-volume drinkers… RR = 0.90, 95% CI [0.76, 1.06]»; using occasional drinkers (not abstainers) as the referent, «there would be no evidence of health protective effects for low-volume drinkers or any other category.»
- the corrected pattern is «more consistent with a linear dose response than a J-shaped curve.»
[EXTRACTED (Stockwell - Moderate Drinkers Mortality Risk 2016) chunk 01, Results; Discussion; Conclusions]
2. Mendelian randomization (Millwood). Genetic variants (ALDH2 rs671, ADH1B) that strongly lower alcohol tolerance act as instruments free of reverse causation and lifestyle confounding. The genotype-predicted (causal) relationship is monotonic, with no protective lower arm:
- ischaemic stroke «RR per 280 g per week 1.27 (1.13-1.43)»; intracerebral haemorrhage «1.58 (1.36-1.84)»; total stroke «1.38 (1.26-1.51)» — «no suggestion of increased stroke risk at very low levels» that would indicate an abstinence penalty, and «no material deviation from log-linear relationships.»
- the causal mechanism is shared by both methods where the observational result is real: blood pressure rises «4.8 mm Hg (4.5-5.1) per 280 g per week» (conventional) and «4.3 mm Hg (3.7-4.9)» (genetic) — convergent, so the confounding is specific to the protective claim, not to alcohol’s BP effect.
[EXTRACTED (Millwood - Alcohol and Vascular Disease Genetic Evidence 2019) chunk 01, Results]
Millwood’s verdict: «the apparently protective effects of moderate alcohol intake against stroke are not mainly caused by alcohol itself, and are largely artifacts of reverse causation and confounding.» Stockwell’s: «low-volume alcohol consumption has no net mortality benefit compared with lifetime abstention or occasional drinking.» [EXTRACTED (Millwood - Alcohol and Vascular Disease Genetic Evidence 2019) chunk 01, Research in context; (Stockwell - Moderate Drinkers Mortality Risk 2016) chunk 01, Conclusions]
Two independent methods, one conclusion [E-independent]
| Parameter | Stockwell 2016 | Millwood 2019 | Same claim? |
|---|---|---|---|
| Method | meta-analysis, bias-corrected | Mendelian randomization (genetic instruments) | independent — different data, methods, populations |
| Outcome | all-cause mortality | stroke, myocardial infarction | NO — different outcomes |
| Moderate-drinking effect | RR 0.97 (0.88-1.07), ns | monotonic harm (stroke); no protective arm | — |
| The claim reached | no net protection from low-volume drinking | protective J-arm is non-causal | YES — moderate drinking is not cardioprotective |
The convergence is on the qualitative claim (the protective lower arm is not causal), reached by a bias-correction route and a genetic route that share no data or lineage and neither references the other as antecedent — a genuine independent-backing lift, not a shared-study echo. The effect sizes are not matched (different outcomes), so this is an E on the direction, not a pooled magnitude. Corroborated across The U-Shaped Association Artifact.
The updated meta-analysis, and where harm starts [Zhao 2023]
Zhao et al. 2023 updates the observational analysis to 107 studies, 4.8 million people and confirms the artifact finding: fully adjusted, low-volume drinking is «RR, 0.93; 95% CI, 0.85-1.01; P = .07» vs lifetime abstainers and only «a RR of 0.97» against the cleaner occasional-drinker referent — no significant protection. Only «21» of 107 studies were free of abstainer bias, and stripping the covariates drives the low-volume estimate to «0.86 (0.83-0.88)» — the protection is manufactured by the biases.
What it adds that the corpus lacked — an actionable harm threshold, and it is sex-specific. Significant all-cause mortality elevation begins at:
- pooled: 45 g/day — «45 to 64 g per day (RR, 1.19; 95% CI, 1.07-1.32)», rising to «1.35» at
=65 g/day; 25-44 g/day pooled is null (1.05, ns);
- women: from 25 g/day — medium-volume «RR, 1.21; 95% CI, 1.08-1.36», and any drinking is already elevated («1.22; 95% CI, 1.02-1.46»);
- men: from 45 g/day — 25-44 g/day is null for men.
- «Across all levels of alcohol consumption, female drinkers had a higher RR of all-cause mortality than males (P for interaction = .001).»
This is the first how-much-is-too-much number the corpus holds for alcohol, and the sex asymmetry is the decision-relevant part — a woman’s threshold sits at roughly half a man’s.
F, not a third E witness (laundering guard). Zhao 2023 is Stockwell’s own group — it «updates our
earlier systematic review» (its ref 8 is Stockwell - Moderate Drinkers Mortality Risk 2016), same
team and method. It refines the observational arm (more studies, occasional referent, the
threshold); it is not an independent method, so the [E-independent] convergence above stays
Stockwell ∥ Millwood, unchanged.
[EXTRACTED (Zhao - Daily Alcohol Intake and Mortality 2023) chunk 01, Results; Discussion; Table 4]
The honest boundary — stroke is not myocardial infarction
MR shows clear causal harm for stroke and blood pressure, but for myocardial infarction the genetic estimate is null: «RR per 280 g per week 0.96 (0.78-1.18), p=0.69» — «little net effect». Millwood suggests alcohol’s BP harm «could be offset by cardio-protective changes in other factors», and cautions the MI case count was limited so «some real benefit or hazard cannot be excluded». So “alcohol is uniformly harmful” holds for stroke and BP; for coronary heart disease the causal picture is genuinely unresolved, and that is the one place a small real benefit is not excluded. [EXTRACTED (Millwood - Alcohol and Vascular Disease Genetic Evidence 2019) chunk 02, Discussion]
What this probes [PRIOR handle — not scored here]
Alcohol is the canonical instance of the telos’s open [PRIOR] #2 — U/J-shaped associations are
frequently artifacts of reverse causation or confounding. This ingest builds the evidence that in the
alcohol case the prior holds (the protective arm is artifact, shown two ways). Per the ingest
contract, the fabric records this; the [PRIOR] is scored in a separate pass, against this and the
still-open sodium J-hypothesis -> Sodium Intake and Blood Pressure, The U-Shaped Association Artifact.
Limits
- All-cause mortality (Stockwell) and vascular disease (Millwood) are different endpoints — matched only at the level of is moderate drinking protective. Neither covers the other’s outcome set.
- Measurement error flattens, it does not manufacture. Both note self-reported intake is underreported; Millwood states this would make the real dose-response shallower, not create the monotonicity — so it cannot rescue the protective arm.
- Millwood is one MR study in one (East Asian) population; ALDH2 is common there and rare in Europeans, so the instrument transports imperfectly. The convergence with a Western-heavy observational meta-analysis is what carries it.
- Coherence, not validity (R1): the causal read rests on the MR assumptions (instrument validity, no pleiotropy — Millwood checks the latter via women as a negative control).