102,136 Chinese adults free of CVD at baseline, from the China-PAR (Prediction for ASCVD Risk in China) project, followed up to 17 years (777,163 person-years); 4,848 incident CVD cases (1,273 CHD, 2,919 stroke) and 5,511 total deaths. Found U-shaped associations of egg consumption with both incident CVD and all-cause mortality, reference 3-<6 eggs/week. (Full text paywalled; extraction from abstract + confirmed extreme-category HRs, so intermediate-category HRs and the full Discussion are not captured.)
Methodology
Prospective cohort of 102,136 CVD-free adults from the China-PAR project (Prediction for ASCVD Risk in China; an independent large Chinese cohort distinct from China Kadoorie Biobank and CHNS). Egg intake by baseline food-frequency questionnaire, categorised <1, 1-<3, 3-<6 (reference), 6-<10, and >=10 eggs/week. Outcomes: incident CVD (CHD and stroke) and all-cause mortality, confirmed by interviewing participants/proxies and checking hospital records and death certificates. 777,163 person-years, up to 17 y follow-up; cohort-stratified multivariable Cox regression. (Covariate list and subtype-specific HRs not accessible in the free abstract.)
Results
O-108 - China-PAR U-shaped egg-CVD association lowest at 3 to under 6 eggs per week higher at both extremes
Reference (lowest-risk) category 3-<6 eggs/week. Cohort-stratified Cox regression, multivariable-adjusted. Intermediate category HRs (1-<3/week, 6-<10/week) were not accessible (paywalled full text); the reported extremes plus the interior reference establish the U-shape and its thresholds.
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O-109 - China-PAR U-shaped egg-mortality association lowest at 3 to under 6 eggs per week
The mortality U is asymmetric: the low-intake arm (1.29) is steeper than the high-intake arm (1.13), the reverse of the CVD pattern (low 1.22 vs high 1.39). Reference category 3-<6 eggs/week.
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Interpretation
H-44 - An intermediate egg intake of about 3 to 6 per week minimizes CVD and mortality risk with harm at both lower and higher intake
The authors’ conclusion: “moderate egg consumption of 3-<6/week should be recommended for CVD prevention in China.”
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A-41 - Elevated risk at both intake extremes within one cohort refutes any monotone egg-CVD dose-response for this population
A monotone dose-response function is either non-increasing or non-decreasing across the whole intake range. The China-PAR estimates place minimum risk at the interior 3-<6 eggs/week category, with risk rising as intake falls to <1/week (CVD HR 1.22; mortality 1.29) and as it rises to >=10/week (CVD 1.39; mortality 1.13). A function that increases on both sides of an interior minimum is by definition non-monotone.
Therefore neither a “more eggs, lower risk” nor a “more eggs, higher risk” linear model can fit these data; any adequate model must be U-shaped (or at least non-monotone). This is a purely logical consequence of the reported category hazard ratios and holds regardless of their causal interpretation - so if these associations are taken at face value, a single linear egg-CVD coefficient is mis-specified for this population.
Validity (step 6)
status: approved | reason_if_not_false: checked
Traced the load-bearing step directly. Monotone = non-increasing OR non-decreasing across the whole range. The reported category point estimates rise both as intake falls below the interior 3-<6/week minimum (CVD 1.22, mortality 1.29 at <1/week) and as it rises above it (CVD 1.39, mortality 1.13 at >=10/week). A function that increases on both sides of an interior minimum is non-monotone by definition, so no single monotone/linear dose-response can fit. This is a definitional/logical consequence, not a substantive claim. The only candidate undercutting defeater - that overlapping CIs could leave a monotone true function - is disarmed by the argument’s explicit conditioning on the point estimates being “taken at face value”; conditional on the premise (the category HRs as reported), non-monotonicity is definitional. Holds as stated.
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A-42 - The low-intake arm of the U may overstate harm because very low egg intake marks low socioeconomic status and poor health
In a Chinese cohort spanning wide socioeconomic conditions, consuming under one egg per week is an unusually low intake that tends to co-occur with poverty, food insecurity and prevalent poor health, all of which independently raise CVD and mortality risk. A single baseline FFQ also cannot separate people who habitually eat few eggs from those who reduced intake because of pre-existing illness (reverse causation).
Both mechanisms push the low-intake hazard ratios (CVD 1.22, mortality 1.29) upward relative to the true causal effect of low egg intake. The left arm of the U is thus the more confounding-prone half, and the apparent harm of very low intake should be discounted more heavily than the harm at the high-intake end, which is less tied to deprivation. This is a standard consideration for interpreting the low-exposure arm of a nutritional U-shape and does not depend on the exact numbers; it weakens (without eliminating) the low-intake half of the U-shaped reading.
Validity (step 6)
status: approved | reason_if_not_false: checked
Traced the step directly (standard confounding/reverse-causation direction-of-bias reasoning, no specialist formalism). Premises: (i) very low egg intake positively correlates with poverty/food insecurity/poor baseline health, which independently raise CVD and mortality; (ii) a single baseline FFQ conflates habitual low eaters with those who cut intake due to prevailing illness; (iii) the high-intake arm is less tied to deprivation. Conditional on these, a confounder that both raises the outcome and correlates with the exposure category biases that category’s HR upward, and reverse causation adds a further upward push - so the <1/week HR overstates the causal harm of low intake, and the comparative claim (discount the left arm more than the right) follows from premise (iii). The conclusion is already appropriately hedged (“liable to inflation”, “probably overstates”, “weakens without eliminating”). No undercutting defeater survives that does not deny a premise: the only route to reversing the sign of bias would require the SES/health confounders to be net-protective in this cohort, which contradicts premise (i). Holds as stated.
Link to original
relevance_note: A nonlinear, non-monotonic dose-response in an independent large Chinese cohort — direct evidence against reading Kadoorie’s “more eggs = more protective” as generalizing to higher intakes, and a harm signal at both low and high extremes.