Research Review
Not All Numbers Are Equal
Modern health tracking gives you access to dozens of metrics, from daily step counts to sleep scores to blood panel results. But when it comes to predicting how long you will live and, more importantly, how well you will live, only a handful of biomarkers carry the strongest evidence. These are the numbers that longevity researchers, cardiologists, and sports scientists consistently point to as the most meaningful indicators of healthspan.
This guide ranks and explains the biomarkers with the strongest evidence base, covers how to test each one, defines what "good" looks like, and outlines what actually improves them.
VO2 Max: The Single Strongest Predictor
VO2 max measures the maximum amount of oxygen your body can use during intense exercise, expressed in milliliters per kilogram of body weight per minute (ml/kg/min). It reflects the integrated function of your heart, lungs, blood vessels, and skeletal muscle.
A landmark 2018 study published in JAMA Network Open by Mandsager and colleagues analyzed 122,007 patients over a median follow-up of 8.4 years. The findings were striking: elite cardiorespiratory fitness (top 2.3%) was associated with an 80% reduction in all-cause mortality compared to the lowest fitness group. Crucially, there was no upper limit of benefit. Being extremely fit was never associated with increased risk. The mortality hazard associated with low fitness was comparable to, or exceeded, that of smoking, diabetes, and coronary artery disease.
How to test: The gold standard is a graded exercise test with gas exchange analysis (often available at sports medicine clinics for $150 to $300). Apple Watch and Garmin devices provide estimated VO2 max from outdoor workout data, which is useful for tracking trends even if the absolute numbers are less precise.
What good looks like: For adults under 50, a VO2 max above 40 ml/kg/min for men and above 35 ml/kg/min for women is "good." Above 50 and 45 respectively puts you in the "excellent" category. The longevity literature suggests that maintaining a VO2 max in the top 25% for your age and sex is associated with the largest mortality benefit.
How to improve it: High-intensity interval training (HIIT) is the most efficient protocol. Norwegian 4x4 intervals (4 minutes at 90 to 95% max heart rate, 3 minutes recovery, repeated 4 times) have the strongest evidence base for VO2 max improvement. Consistent zone 2 training (60 to 70% max heart rate for 30 to 60 minutes) builds the aerobic base that supports higher-intensity work.
Grip Strength: Surprisingly Powerful
Grip strength, measured with a handheld dynamometer, is one of the most consistent predictors of all-cause mortality across populations. The PURE study, published in The Lancet by Leong and colleagues, followed 139,691 adults across 17 countries and found that every 5 kg decrease in grip strength was associated with a 16% increase in all-cause mortality, a 17% increase in cardiovascular mortality, and a 9% increase in stroke risk. Grip strength was a stronger predictor of death than systolic blood pressure.
Grip strength likely serves as a proxy for overall neuromuscular function, systemic inflammation, and nutritional status. It declines predictably with age, and the rate of decline itself is prognostic.
How to test: A Jamar or Camry hand dynamometer costs $20 to $40 and provides reliable measurements. Test both hands, three attempts each, and use the highest reading.
What good looks like: For men aged 30 to 50, a grip strength above 45 kg is "good" and above 55 kg is "excellent." For women in the same age range, above 30 kg is "good" and above 37 kg is "excellent." Values below 26 kg for men and 18 kg for women are associated with significantly increased mortality risk regardless of age.
How to improve it: Direct grip training (dead hangs, farmer carries, plate pinches) is effective, but compound pulling exercises (deadlifts, rows, pull-ups) also build grip as a secondary benefit. Consistency matters more than intensity.
Lean Body Mass and Muscle Mass
Skeletal muscle is the largest organ system in the body by mass. It is the primary site for glucose disposal (responsible for roughly 80% of insulin-stimulated glucose uptake), a reservoir for amino acids during illness or stress, and a critical determinant of metabolic rate, functional independence, and fall prevention as you age. Low muscle mass is independently associated with increased all-cause mortality, type 2 diabetes risk, cardiovascular events, and cognitive decline.
How to test: DEXA scans provide the gold standard measurement of lean body mass and fat mass ($75 to $200 per scan). Bioimpedance scales (like InBody or Withings) are less precise but useful for tracking trends over time.
What good looks like: Appendicular lean mass index (ALMI, total limb lean mass divided by height squared) above 7.0 kg/m2 for men and above 5.5 kg/m2 for women is the threshold below which sarcopenia risk increases significantly.
How to improve it: Progressive resistance training with adequate protein intake (1.2 to 1.6g per kg body weight daily) is the only reliable way to build and maintain muscle mass. There are no shortcuts.
Heart Rate Variability (HRV)
HRV measures the variation in time between consecutive heartbeats. Higher HRV generally reflects a well-functioning autonomic nervous system with strong parasympathetic (rest-and-recover) activity. HRV declines with age, and lower HRV is associated with increased cardiovascular risk, systemic inflammation, and all-cause mortality.
How to test: Wearables including the Oura Ring, Apple Watch, Whoop, and Garmin devices all track HRV, typically during sleep. Morning HRV readings taken in a consistent position (lying down, immediately upon waking) provide the most reliable data. Vora aggregates HRV data from multiple wearable sources and tracks your 7-day rolling average, which is more meaningful than any single reading.
What good looks like: HRV is highly individual. Population averages for RMSSD (the most common metric) range from 20 to 100+ ms depending on age, sex, and fitness level. Rather than chasing an absolute number, focus on your personal trend: a stable or gradually increasing 7-day average is a positive sign, while a declining trend may signal overtraining, poor sleep, or chronic stress.
How to improve it: Aerobic exercise, quality sleep, stress management (breathwork, meditation), and moderate alcohol reduction all improve HRV over time. Overtraining, sleep deprivation, and chronic stress suppress it.
Resting Heart Rate
A lower resting heart rate generally reflects better cardiovascular fitness and more efficient cardiac function. Population studies consistently show that resting heart rates above 80 bpm are associated with increased cardiovascular and all-cause mortality risk, while rates in the 50 to 65 bpm range are associated with the best outcomes in healthy adults.
How to test: Any wearable device or even a manual pulse check can measure resting heart rate. For the most consistent readings, measure first thing in the morning before getting out of bed.
How to improve it: Regular aerobic exercise is the primary driver. Consistent zone 2 training (3 to 5 sessions per week of 30 to 60 minutes at conversational pace) typically produces noticeable reductions in resting heart rate within 4 to 8 weeks.
Fasting Insulin and Glucose
Metabolic health is foundational to longevity. Fasting glucose is the standard screening metric, but fasting insulin is arguably more informative because it can detect insulin resistance years before glucose levels become abnormal. Elevated fasting insulin, even with normal glucose, is associated with increased cardiovascular risk, cancer incidence, and cognitive decline.
How to test: Standard blood work through your physician. Request both fasting glucose and fasting insulin specifically, as insulin is not always included in routine panels.
What good looks like: Fasting glucose below 90 mg/dL and fasting insulin below 8 uIU/mL are considered optimal by most longevity-focused clinicians. A HOMA-IR score (calculated from glucose and insulin) below 1.0 indicates excellent insulin sensitivity.
How to improve it: Resistance training (which increases glucose uptake into muscle), maintaining healthy muscle mass, reducing refined carbohydrate intake, adequate sleep, and maintaining a healthy body composition all improve insulin sensitivity.
ApoB (Apolipoprotein B)
ApoB is a protein found on the surface of all atherogenic (artery-damaging) lipoprotein particles, including LDL, VLDL, and Lp(a). Unlike standard LDL cholesterol, which measures the cholesterol content of LDL particles, ApoB counts the actual number of atherogenic particles circulating in your blood. This makes it a more accurate predictor of cardiovascular risk because it is the number of particles, not the cholesterol they carry, that drives plaque formation.
How to test: A standard blood test available through most physicians. It is increasingly included in advanced lipid panels, though you may need to request it specifically.
What good looks like: Below 90 mg/dL is "acceptable" for most adults. Below 60 mg/dL is considered optimal by many cardiologists focused on atherosclerosis prevention. For individuals with existing cardiovascular disease or high genetic risk, targets below 50 mg/dL may be appropriate.
How to improve it: Diet modifications (reducing saturated fat, increasing fiber), regular exercise, and maintaining a healthy weight can modestly reduce ApoB. For significant reductions, statin medications and PCSK9 inhibitors are the most effective interventions and should be discussed with a physician.
Blood Pressure
Hypertension remains the single largest modifiable risk factor for cardiovascular disease globally. Even modest elevations in blood pressure sustained over decades dramatically increase the risk of stroke, heart failure, kidney disease, and dementia.
What good looks like: Below 120/80 mmHg is optimal. The 120 to 129 systolic range is "elevated," and anything above 130/80 meets the current definition of hypertension.
How to improve it: Regular aerobic exercise, maintaining a healthy weight, reducing sodium intake, increasing potassium intake (fruits, vegetables), limiting alcohol, and managing stress all contribute to blood pressure management. Medication is appropriate when lifestyle measures are insufficient.
Building Your Personal Dashboard
The most practical approach to longevity tracking is to combine wearable-trackable metrics (VO2 max, HRV, resting heart rate, activity levels) with periodic blood work (fasting insulin, glucose, ApoB, blood pressure) and annual or semi-annual body composition assessments. This creates a multi-layered view of your health trajectory that no single metric can provide.
Vora already integrates the wearable side of this equation, pulling HRV, resting heart rate, sleep data, and activity metrics from devices like the Oura Ring, Apple Watch, and Garmin to provide a continuous recovery and readiness signal. Combined with periodic lab work, this gives you a comprehensive picture of the biomarkers that actually predict how long and how well you will live.