Research Library

The evidence behind every factor Halo asks about

Search and filter the primary research behind Halo's longevity model — what the evidence shows, how strong it is, and where its limits are — with a link to every original study.

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Strong evidence
Moderate evidence
Limited evidence

Evidence quality is graded per record, not for the library as a whole. Each card names the specific reliability or bias concerns that apply — self-report accuracy, reverse causation, confounding — next to the claim they qualify.

These summarise population-level associations. They describe patterns across large groups of people, not a prediction about you specifically.

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34 results

Tobacco smoking and all-cause mortality in a large Australian cohort study

Strong
SmokingObservational evidenceReverse causation riskSelf-report bias
Cohort study
Never smoker = reference; current smoking ~2.18–2.81× mortality in large cohorts; former smokers can approach never-smoker risk after prolonged cessation
Causal status: Causal support strong; mortality evidence mostly prospective
Reliability / bias notes: Self-report; pack-years and cessation timing matter; reverse causation can affect recent quitters
Banks et al · BMC Med · 2015 · PMID 25857449
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Gamma-glutamyltransferase is associated with cardiovascular and all-cause mortality: a meta-analysis of prospective cohort studies

Moderate
Liver Function (GGT)Meta-analysisObservational evidence
Meta-analysis
Highest vs lowest GGT quartile associated with 56% higher all-cause mortality (pooled RR 1.56, 95% CI 1.34–1.83) across 7 prospective cohorts, 273,141 participants
Causal status: Associational; proposed independent of alcohol intake but mechanism as a general oxidative-stress/liver marker not fully causal
Reliability / bias notes: GGT is nonspecific (affected by alcohol, medications, fatty liver); Asian subgroup result not significant
Du et al · Prev Med · 2013 · PMID 23571185
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Family history of premature death and risk of early onset cardiovascular disease

Strong for susceptibility
Hereditary Cardiovascular diseaseObservational evidence
Observational study
Danish cohort: premature family CVD death IRR ~1.72 for any CVD, ~2.21 for IHD; multiple affected relatives much higher
Causal status: Association/genetic + shared environment
Reliability / bias notes: Family-history accuracy; incomplete pedigree; mixed genetic and shared behavioural pathways
Ranthe et al · JACC · 2012 · PMID 22917005
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Do seat belts and air bags reduce mortality and injury severity after car accidents?

Strong for injury mortality
Seat belt useInterventional / RCT evidence
Observational study
Front-seat seat-belt use reduces fatal/nonfatal injury risk by ~60%; trauma database mortality OR ~0.49 vs no restraint
Causal status: Strong causal/interventional evidence for crash injury prevention
Reliability / bias notes: Crash-conditioned evidence; risk-taking behaviours correlated with non-use
Cummins et al. · 2011 · PMID 21720604
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C-reactive protein concentration and risk of coronary heart disease, stroke, and mortality: an individual participant meta-analysis

Strong
C-reactive protein (CRP)Confounding riskMeta-analysisObservational evidence
Meta-analysis
Each 3-fold (1-SD) higher log-CRP associated with 1.55x non-vascular mortality (95% CI 1.41–1.69) and similar magnitude for vascular mortality, in an individual-participant meta-analysis of 160,309 people across 54 studies
Causal status: Causal role debated; CRP likely partly a marker of underlying inflammation/disease rather than a direct cause
Reliability / bias notes: Association attenuates but persists after adjusting for conventional risk factors and fibrinogen; residual confounding by subclinical illness possible
Emerging Risk Factors Collaboration (Kaptoge et al) · Lancet · 2010 · PMID 20031199
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Glycated hemoglobin, diabetes, and cardiovascular risk in nondiabetic adults

Strong
HbA1cObservational evidenceReverse causation risk
Observational study
In nondiabetic adults, glycated hemoglobin showed a J-shaped association with death from any cause, remaining significant after adjustment for fasting glucose, in the ARIC cohort (n=11,092)
Causal status: Causal support strong for diabetes/CVD risk; all-cause mortality relationship J-shaped, so causal direction less clear at low HbA1c
Reliability / bias notes: J-shaped curve means very low HbA1c also carries excess mortality risk, likely reflecting reverse causation/frailty; overlaps with the separate diagnosed-diabetes question, so effects are kept modest to avoid double-counting the same underlying condition
Selvin et al · N Engl J Med · 2010 · PMID 20200384
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Mobile phone use and motor vehicle crash risk / hospital attendance

Moderate for crash risk; limited for mortality
Phone use while drivingObservational evidenceSelf-report bias
Observational study
Crash case-crossover OR 4.1 for phone use within 5 min before crash; culpability OR 1.70 in another study
Causal status: Strong causal plausibility for crash impairment; direct mortality estimate limited
Reliability / bias notes: Self-report/recall; exposure definition; no robust all-cause mortality coefficient
McEvoy et al. · 2007 · PMID 17920840
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Chronic kidney disease and the risks of death, cardiovascular events, and hospitalization

Strong
Kidney Function (eGFR)Confounding riskObservational evidence
Observational study
Adjusted death risk rose stepwise as eGFR fell below 60 mL/min/1.73m2, from HR 1.2 (eGFR 45–59) up to HR 5.9 (eGFR <15), in a cohort of 1.12 million adults
Causal status: Causal support strong; graded, dose-dependent association independent of comorbidities
Reliability / bias notes: Single-measurement creatinine-based eGFR; residual confounding by unmeasured comorbidity possible
Go et al · N Engl J Med · 2004 · PMID 15385656
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Reduced heart rate variability and mortality risk in an elderly cohort. The Framingham Heart Study

Moderate
Heart Rate VariabilityObservational evidence
Cohort study
1-SD decrement in low-frequency HRV power associated with 1.70x greater all-cause mortality hazard (95% CI 1.37–2.09) over 4 years in an elderly community cohort
Causal status: Associational; reflects autonomic dysfunction, prognostic value shown independent of traditional risk factors
Reliability / bias notes: Older, smaller cohort (n=736, 74 deaths); short 2-hour ECG recording window; results in elderly may not generalize to younger adults
Tsuji et al · Circulation · 1994 · PMID 8044959
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Kivimäki et al. Job strain and mortality / coronary heart disease evidence (multicohort analysis)

Moderate for defined job strain; limited for generic stress
StressConfounding riskObservational evidenceReverse causation risk
Cohort study
Job strain meta-analysis: CHD RR ~1.26; multicohort mortality HR 1.68 in men with cardiometabolic disease
Causal status: Association
Reliability / bias notes: Construct heterogeneity; socioeconomic confounding; reverse causation
PMID 29884468
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