Biomarkers

Apnea-Hypopnea Index (AHI)

Average number of breathing events per hour of sleep. Defines obstructive sleep apnea severity — a major modifiable cardiovascular, metabolic, and cognitive risk factor.

ApoA1 and ApoB/ApoA1 Ratio

Apolipoprotein A1 is the principal protein on HDL particles. The ApoB/ApoA1 ratio combines atherogenic and protective particle counts into a single risk score validated in INTERHEART.

ApoB (Apolipoprotein B)

A single-particle count of all atherogenic lipoproteins. Modern lipidology treats it as the principal cardiovascular-risk lipid marker, superior to LDL-C in discordant cases.

Blood Pressure

The most heavily-evidenced modifiable risk factor in adults. Tight control reduces cardiovascular events and cognitive decline; what counts as "tight" continues to evolve downward.

Carotid Intima-Media Thickness (CIMT)

Ultrasound measurement of the inner two layers of the carotid artery wall. A non-invasive marker of subclinical atherosclerosis and vascular age.

Chair-Rise Test (Sit-to-Stand)

Time or count of stand-up repetitions from a chair without using hands. Captures lower-body strength, balance, and falls risk in a low-tech test.

Coronary Artery Calcium (CAC) Score

A low-dose chest CT measurement of calcified coronary plaque. The strongest single test for personalised cardiovascular risk in middle age.

Cortisol (4-Point Salivary)

Four salivary cortisol measurements across a day to characterise diurnal rhythm. More informative than single serum cortisol for HPA-axis assessment.

Cystatin C

A small protein produced uniformly by nucleated cells that is freely filtered by the kidney. Often a better estimator of GFR than creatinine, especially in low-muscle adults.

DEXA Scan (Body Composition + Bone Density)

Dual-energy X-ray absorptiometry — the reference body-composition test for lean mass, visceral fat, and bone density.

eGFR (Estimated Glomerular Filtration Rate)

The primary measure of kidney function. Declines with age; the rate of decline is the actionable signal.

Epigenetic Clocks (Horvath, GrimAge, DunedinPACE)

DNA-methylation-based estimators of biological age and the rate of biological aging. The most-used biomarkers in geroscience research today.

Estradiol

The principal estrogen in reproductive-age women; falls sharply at menopause. Interpretation differs between pre-menopausal cycle-monitoring and post-menopausal HRT contexts.

Fasting Insulin & HOMA-IR

Fasting insulin (and the derived HOMA-IR index) detect insulin resistance years before fasting glucose or HbA1c become abnormal.

Ferritin (and Iron Studies)

Marker of body iron stores and an acute-phase reactant. Both deficiency and overload increase mortality. Optimal sits in a narrow band.

Folate (B9)

Essential B vitamin for one-carbon metabolism. Deficiency causes megaloblastic anaemia; supplementation in pregnancy prevents neural tube defects. Caution with unmetabolised folic acid in high-dose supplementers.

Frailty Index

A composite "deficits accumulated" score that captures biological age better than any single biomarker in older adults.

Gait Speed

Usual walking speed over a short measured course. One of the most predictive single tests for survival, hospitalisation, and functional decline in older adults.

GDF-15

Stress-induced cytokine that rises with age, chronic disease, and mitochondrial dysfunction. Among the strongest single-protein predictors of all-cause mortality in older adults.

GlycA

NMR-derived measure of glycosylated acute-phase proteins. Captures a more stable component of chronic inflammation than hsCRP and predicts long-term cardiovascular and mortality risk.

GlycanAge

A biological-age estimator based on the glycosylation pattern of immunoglobulin G (IgG), reflecting chronic inflammatory state.

Grip Strength

A simple handheld dynamometer reading that predicts all-cause mortality and cardiovascular events better than systolic blood pressure in some cohorts.

HbA1c (Glycated Haemoglobin)

A 3-month average of blood glucose exposure. Beyond diabetes diagnosis, HbA1c levels in the "normal-high" range track future cardiovascular and dementia risk.

HDL Cholesterol (HDL-C)

Historically the 'good cholesterol'. Modern Mendelian-randomisation work shows isolated HDL changes don't cause cardiovascular risk shifts — HDL is a marker of overall metabolic health more than a direct lever.

Heart Rate Variability (HRV)

Beat-to-beat variation in heart rate, an indirect readout of autonomic-nervous-system balance. Higher HRV correlates with cardiovascular health and recovery; trends matter more than absolute numbers.

High-Sensitivity Troponin (hs-Trop)

Ultra-sensitive measurement of cardiac troponin T or I. Originally used to diagnose MI; now low-level chronic elevations predict cardiovascular and all-cause mortality in apparently healthy adults.

Homocysteine

A sulfur-containing amino acid intermediate; elevated levels associate with cardiovascular and cognitive risk, often reflecting B-vitamin (B12, folate, B6) inadequacy.

hsCRP (High-Sensitivity C-Reactive Protein)

Sensitive blood marker of systemic inflammation that predicts cardiovascular events and tracks "inflammaging".

IGF-1 (Insulin-Like Growth Factor 1)

The principal mediator of growth hormone effects. Low childhood IGF-1 stunts growth; high adult IGF-1 promotes cancer; very low adult IGF-1 associates with frailty. The optimal range is a balance.

IL-6 (Interleukin-6)

A central inflammatory cytokine whose chronic elevation drives inflammaging, hepatic CRP synthesis, and a broad range of age-related diseases.

LDL Cholesterol (LDL-C)

The cholesterol mass carried in low-density lipoprotein particles. Historically the headline lipid marker; superseded by apoB in modern lipidology when the two disagree.

LDL Particle Number (LDL-P)

Direct count of LDL particles by NMR spectroscopy. Equivalent information to apoB; chiefly useful when apoB testing isn't readily available.

Lipoprotein(a) — Lp(a)

A genetically determined atherogenic lipoprotein. Elevated Lp(a) affects ~20% of adults and is an independent cardiovascular risk factor not addressed by lifestyle.

Methylmalonic Acid (MMA)

Sensitive metabolic marker of vitamin B12 status. Elevated MMA in the presence of borderline B12 confirms functional deficiency before clinical signs appear.

MoCA (Montreal Cognitive Assessment)

10-minute cognitive screening test. More sensitive than the MMSE for mild cognitive impairment and useful as a serial measure to track cognitive trajectory.

Non-HDL Cholesterol

Total cholesterol minus HDL — a calculation that approximates atherogenic cholesterol burden when apoB is unavailable. Better than LDL-C alone, especially with elevated triglycerides.

NT-proBNP (and BNP)

Cleavage product of brain natriuretic peptide released by ventricular stretch. Best blood marker of cardiac filling pressure and heart failure; rising levels predict events well before symptoms.

PhenoAge

A biological-age score combining nine standard clinical biomarkers, predictive of mortality and computable from a routine blood panel.

Pulse-Wave Velocity (Arterial Stiffness)

Speed of the arterial pressure wave between two arterial sites. Higher PWV = stiffer arteries = older biological vascular age and elevated cardiovascular risk.

RBC Magnesium

Red-blood-cell magnesium reflects intracellular stores better than serum magnesium, which is tightly regulated and stays normal even with substantial deficiency.

Resting Heart Rate (RHR)

One of the simplest and most powerful predictors of all-cause mortality. Lower (within physiological range) is generally better.

Sex Hormone-Binding Globulin (SHBG)

Liver-produced glycoprotein that binds sex hormones in circulation. SHBG levels alter the free fraction of testosterone and estradiol — and rise/fall with insulin resistance, age, and oestrogen state.

Telomere Length

A noisy biomarker of cellular replicative history and biological age. Useful at population scale; less informative for individuals from a single timepoint.

Testosterone (Total and Free)

The principal androgen in men; declines ~1–2%/year after age 30. Low testosterone with symptoms warrants evaluation; treating asymptomatic "low-normal" levels has unclear benefit.

Thyroid Panel (TSH, fT4, fT3, antibodies)

TSH alone is the screening test; full panel (free T4, free T3, TPO antibodies) is needed when symptoms or atypical patterns appear.

Triglyceride/HDL Ratio

A simple ratio (TG ÷ HDL, both in mg/dL) that serves as a useful proxy for insulin resistance and small-dense LDL when more direct tests aren't available.

Triglycerides

Plasma triglycerides reflect VLDL and chylomicron remnant burden. Modestly atherogenic at typical levels; cardiovascular outcomes improve when triglyceride-lowering coincides with apoB reduction.

Uric Acid

End-product of purine metabolism; high levels cause gout and associate with cardiovascular, renal, and metabolic disease. A simple, undervalued marker.

Vitamin B12 (Cobalamin)

Essential cofactor for DNA synthesis, methylation, and myelin maintenance. Deficiency causes anaemia and irreversible neurological damage; risk concentrated in older adults, vegans, and metformin/PPI users.

VO2max

Maximal rate of oxygen uptake during exercise — among the strongest single predictors of all-cause mortality across the adult lifespan.