epigenetic_clocks: one bounded, context-dependent signal across receipts

Source literature boundary memo

Research question

Across retrieved fact-level receipts for epigenetic_clocks, which endpoints show directionally favorable versus null/non-convergent signals, and what matched PICO remains untested?

Selection criteria

The source-literature fallback selected epigenetic_clocks because the domain snapshot exposed enough fact-backed, topic-overlapping papers. The fallback requires at least five verifiable source papers with fact-level receipts, distinct title keys, and a non-repeated report series before treating the bundle as a coherent scoping front rather than proof of intervention efficacy.

Boundary map

• Dental Ageing Offers New Insights Into the First Epigenetic Clock for Common Dolphins (Delphinus delphis). [primary; 2025] doi:10.1002/ece3.72424
  • Finding: The hybrid model using the relaxed subset produced a MAE of 2.61 years
  • Population: Common dolphins (Delphinus delphis)
  • Intervention/exposure: Hybrid epigenetic clock
  • Comparator: dental age
• Cross‐tissue comparison of epigenetic aging clocks in humans [primary; 2025] doi:10.1111/acel.14451
  • Finding: average differences of almost 30 years observed in some age clocks
  • Population: 83 individuals aged 9-70 years
  • Intervention/exposure: blood-derived epigenetic clocks
  • Comparator: oral-based tissues
• Longitudinal Study of DNA Methylation and Epigenetic Clocks Prior to and Following Test-Confirmed COVID-19 and mRNA Vaccination [primary; 2022] doi:10.3389/fgene.2022.819749
  • Finding: Principal component-based epigenetic clock estimates of PhenoAge significantly increased in people over 50 following infection by an average of 2.1 years.
  • Population: people over 50 following test-confirmed non-hospitalized COVID-19
  • Intervention/exposure: COVID-19 infection
  • Comparator: prior to infection
• DNA methylation clocks for dogs and humans [primary; 2022] doi:10.1073/pnas.2120887119
  • Finding: two highly accurate human–dog dual species epigenetic clocks (R = 0.97)
  • Population: humans and dogs
  • Intervention/exposure: none
• Variations in Innate Immune Cell Subtypes Correlate with Epigenetic Clocks, Inflammaging and Health Outcomes. [primary; 2025] doi:10.1002/advs.202505922
  • Finding: up to 40% of an epigenetic clock's accuracy in blood being driven by age‐related shifts in lymphocyte subsets
  • Population: blood
  • Intervention/exposure: epigenetic clock

Source synthesis

This receipt-backed scoping note has one bounded signal: epigenetic_clocks shows context-dependent, not uniformly convergent associations across this 5-source primary bundle (2022-2025). Grouped by direction, other/mixed: 5 receipt(s). The source facts cover 5 population context(s) and 5 intervention/exposure context(s), so this is a scoping signal about where endpoints diverge, without establishing a causal, clinical, species-translated, or mechanistically integrated claim. The listed effect sizes remain source-specific across endpoints and populations; they are not pooled or averaged. Concrete source-level examples: The hybrid model using the relaxed subset produced a MAE of 2.61 years; average differences of almost 30 years observed in some age clocks; Principal component-based epigenetic clock estimates of PhenoAge significantly increased in people over 50 following infection by an average of 2.1 years.

Directional grouping

• directionally favorable: epigenetic_clocks is the intervention/exposure and the reported clinical endpoint favors that arm.

• comparator/not favorable: epigenetic_clocks is the comparator arm; the label is limited to that head-to-head endpoint.

• economic/context only: the receipt reports cost, QALY, or economic context rather than a clinical efficacy endpoint.

• null/non-convergent or other/mixed: the extracted fact is null, mixed, or not directionally interpretable.

• other/mixed: Dental Ageing Offers New Insights Into the First Epigenetic Clock for Common Dolphins (Delphinus delphis). — The hybrid model using the relaxed subset produced a MAE of 2.61 years

• other/mixed: Cross‐tissue comparison of epigenetic aging clocks in humans — average differences of almost 30 years observed in some age clocks

• other/mixed: Longitudinal Study of DNA Methylation and Epigenetic Clocks Prior to and Following Test-Confirmed COVID-19 and mRNA Vaccination — Principal component-based epigenetic clock estimates of PhenoAge significantly increased in people over 50 following infection by an average of 2.1 years.

• other/mixed: DNA methylation clocks for dogs and humans — two highly accurate human–dog dual species epigenetic clocks (R = 0.97)

• other/mixed: Variations in Innate Immune Cell Subtypes Correlate with Epigenetic Clocks, Inflammaging and Health Outcomes. — up to 40% of an epigenetic clock's accuracy in blood being driven by age‐related shifts in lymphocyte subsets

Specific moderators in this bundle are outcome type (Median Absolute Error (MAE); accuracy), population/indication (83 individuals aged 9-70 years; Common dolphins (Delphinus delphis); blood; humans and dogs; people over 50 following test-confirmed non-hospitalized COVID-19), study design/evidence type (primary).

Context separation

The selected receipts group because each carries a fact-level extraction for epigenetic_clocks; they separate by context (other source context) and endpoint, so they are not interchangeable evidence for one pooled claim.

Boundary limits

Source-literature boundary for epigenetic_clocks: the listed sources define one bounded, context-dependent signal across separate source contexts. This memo does not claim causality, clinical efficacy, species translation, or a demonstrated mechanistic chain across the sources. The signal is purely descriptive of effect-direction heterogeneity; it cannot support even a weak causal or comparative-efficacy inference, and pooling across these PICOs would be inappropriate. Routing domain longevity_research is publication-lane metadata only; the source scope here is defined by the selected epigenetic_clocks receipts.

Next gaps

No source in this fallback bundle tests human clinical endpoints. A stronger memo needs one matched PICO, for example: population=Common dolphins (Delphinus delphis); intervention/exposure=Hybrid epigenetic clock; comparator=dental age; outcome=Median Absolute Error (MAE). If epigenetic_clocks is promoted beyond a scoping note, the next run should select sources sharing one context family rather than mixing other source context.