Every pillar on this site uses terms that don’t get defined on first use, because the post that introduced them assumed you’d look it up. This page is that lookup. Plain-language definitions for the recurring biomarkers, nervous-system terms, and site-coined concepts — nothing here is medical advice, just a shared reference.
Precision Longevity terms
ApoB (Apolipoprotein B) — A protein found on every artery-clogging lipoprotein particle in your blood. Because it counts particles rather than the cholesterol packed inside them, many cardiologists consider it a more direct measure of cardiovascular risk than standard LDL cholesterol.
LDL-C — The amount of cholesterol carried inside low-density lipoprotein (LDL) particles, the number on a standard lipid panel. It measures cholesterol mass, while ApoB counts the particles themselves.
hs-CRP (high-sensitivity C-reactive protein) — A blood marker of low-grade, chronic inflammation. Unlike the CRP test used to catch acute infections, the “high-sensitivity” version is sensitive enough to flag the quiet, long-running inflammation linked to cardiovascular and metabolic disease.
Sarcopenia — The age-related loss of muscle mass and strength. It’s gradual, often invisible on a scale, and the reason “muscle as a retirement plan” shows up repeatedly across Precision Longevity content — strength is what keeps independence intact later in life.
Grip strength — A simple, low-tech proxy for overall muscular and functional health, often used in research as a predictor of broader health outcomes because it correlates with total-body strength and physical resilience.
Resistance training — Exercise in which your muscles work against a load, such as weights, bands or your own body weight. It is the type of training that does the most to build muscle.
SHBG (sex hormone-binding globulin) — A protein that binds circulating testosterone and estrogen, making them biologically inactive while bound. SHBG rises with age, which is why “total testosterone” alone can be a misleading number without it.
Hypogonadism — The clinical term for low testosterone. Diagnosing it requires both a consistently low lab result and real symptoms — a low number alone, with no symptoms, isn’t a diagnosis.
STRAW+10 — The medical framework doctors use to stage perimenopause and menopause, based on menstrual cycle changes and hormone markers rather than symptoms alone.
Timing hypothesis — The finding that hormone replacement therapy’s cardiovascular risk depends heavily on when a woman starts it relative to menopause — lower risk starting within 10 years of menopause and under age 60, higher risk starting later.
Bioidentical hormones — Hormone formulations molecularly identical to what the body produces. The word describes chemical structure, not a different safety profile — compounded “bioidentical” products also skip the dosing consistency and safety monitoring FDA-regulated products go through.
MACE (major adverse cardiac events) — The standard trial endpoint for serious heart problems (heart attack, stroke, cardiovascular death) used to measure a treatment’s cardiovascular safety.
Endothelial dysfunction — When the thin lining of your blood vessels stops widening and relaxing as readily as it should. Researchers often treat it as an early sign of vascular strain, and measure it by how much an artery opens up after a brief pause in blood flow.
Periodontitis — Severe gum disease: ongoing infection and inflammation that damages gum tissue and the bone holding your teeth in place. It usually starts as milder gum inflammation (gingivitis), which is why bleeding gums are worth taking seriously.
Fat-free mass — Everything in your body that isn’t fat: muscle, bone, organs and water. Studies on weight loss often track it as a stand-in for muscle, though it’s an imperfect one.
VO2peak — The highest rate at which your body can take in and use oxygen during hard exercise. It’s a standard lab measure of aerobic fitness.
Mild cognitive impairment (MCI) — Memory or thinking problems that are noticeable and measurable beyond normal aging, but not severe enough to take away a person’s independence in daily life. Some people with MCI go on to develop dementia; others stay stable or improve.
Episodic memory — Memory for specific personal experiences — what happened, where, and when, like a conversation you had last week. It is often one of the first kinds of memory to slip in Alzheimer’s disease.
White matter hyperintensities — Bright spots on certain brain MRI scans that mark damaged areas in the brain’s white matter, the wiring that connects brain regions. They are usually tied to disease of the brain’s small blood vessels, become more common with age and high blood pressure, and larger amounts are linked to higher stroke and dementia risk.
Surgical menopause — Menopause caused by surgically removing both ovaries (bilateral oophorectomy), which stops ovarian hormone production all at once. Natural, or spontaneous, menopause happens gradually as the ovaries wind down on their own.
Glycosylation (hyperglycosylation) — The process cells use to attach sugar chains to proteins and fats, which shapes how those molecules fold and work. Hyperglycosylation means more of this sugar-tagging than normal.
Vasomotor symptoms — The clinical name for hot flashes and night sweats, the sudden waves of heat and sweating that come from changes in how the brain regulates body temperature during the menopause transition. They can last years, not weeks.
Perimenopause — The transition leading up to menopause, when hormone levels and cycles start to change and symptoms such as hot flashes, poor sleep and aches can begin. It ends 12 months after the final period. For the formal staging system, see STRAW+10.
Growth hormone (GH) — A hormone made by the pituitary gland, released in pulses and closely tied to sleep, that helps regulate growth, body composition and metabolism. Its release drops with age.
Polygenic risk score — A single number that adds up the small effects of many common gene variants to estimate how strongly someone’s DNA predisposes them to a condition. It shows a tendency in a group, not a diagnosis or a certainty for one person. Two people with the same score can have very different outcomes.
BPSD (behavioral and psychological symptoms of dementia) — The non-memory symptoms that often come with dementia, such as apathy, agitation, anxiety, depression, restlessness and sleep or appetite changes. They affect residents and caregivers, and they are often the main reason families seek extra help.
Metabolic adaptation — The drop in the calories you burn at rest after weight loss, beyond what your smaller body size alone would predict. It is a normal response to losing weight and can persist for years, which is one reason maintaining a loss takes planning.
Hunger hormones — The chemical signals, including leptin, ghrelin and peptide YY, that tell your brain whether you are full or hungry. After weight loss, studies find these signals shift toward more hunger and stay shifted for at least a year.
Gut microbiome — The community of bacteria and other microbes living in your digestive tract. It is linked to digestion, immune function and inflammation, but research on how it affects body weight in people is still early.
Time-restricted eating — Eating all your food inside a set daily window, for example 10 hours, and nothing outside it. Unlike calorie counting, it changes when you eat, not necessarily what or how much.
Glucose tolerance — How well your body clears sugar from your blood after you eat. Poor glucose tolerance means blood sugar stays high longer and is an early sign of metabolic strain.
Healthspan — The number of years you stay healthy and able to do what you want. Lifespan only counts years alive; healthspan counts the years you can use.
NAD+ — A molecule every cell uses to turn food into energy. Supplements such as nicotinamide riboside are sold as “NAD+ boosters” because the body can use them to make more of it.
Surrogate marker — A lab number used as a stand-in for an outcome that matters more, such as a blood level standing in for how well or how long you live. A marker can move without the outcome moving.
Insulin resistance — When your cells respond less to insulin, so your body has to make more of it to move sugar out of your blood. It often develops years before type 2 diabetes and can exist while blood sugar still looks normal.
Visceral fat — Fat stored deep in the abdomen, around organs such as the liver and intestines, as opposed to the fat just under the skin. Waist circumference is a simple, rough way to keep an eye on it.
Melanoma — The skin cancer most likely to spread to other parts of the body. It starts in the cells that make pigment, so it often shows up as a new or changing dark spot, though it can also be pink, red or skin-colored. Found early, it is highly treatable.
Keratinocyte carcinoma — The medical name for basal cell and squamous cell skin cancers, formerly called nonmelanoma skin cancer. They start in the skin’s outer cells, are the most common skin cancers, and usually grow more slowly than melanoma.
Ugly duckling sign — A way to spot a suspicious mole by comparison: most of your moles look alike, so the one that looks different from the rest is the one worth showing a dermatologist.
Proteomics — The large-scale measurement of proteins, the molecules that do most of the work in your cells. A proteomic blood test measures hundreds or thousands of proteins at once, far more than the handful in a standard blood panel.
Autophagy — The cell’s built-in system for breaking down and recycling worn-out proteins and other parts. It works in several forms, and researchers count disabled autophagy among the hallmarks of aging.
Cellular senescence — A state in which damaged cells stop dividing but don’t die. They release inflammatory signals and build up in tissues with age, which is why they are sometimes called “zombie cells.”
Alternate-day fasting — An eating pattern that alternates fasting days, with little or no food, with ordinary eating days. Researchers study it as one way to cut calories, usually comparing it with eating every day.
Biological age (aging clock) — An estimate of how old your body, or one organ system, looks compared with the years on your calendar. Researchers build “aging clocks” with machine-learning models that use measures such as brain imaging or blood markers, then study the gap between biological and calendar age.
Body mass index (BMI) — A number worked out from your weight divided by your height squared, used as a quick screening measure of weight category. It can’t tell muscle from fat, so it says little about body composition on its own.
DEXA scan (dual-energy X-ray absorptiometry) — A scan that uses very low-dose X-rays to measure bone density and to split body weight into fat, lean tissue and bone.
Grey matter — Brain tissue made up mostly of nerve-cell bodies, where much of the brain’s processing happens. MRI studies track how its volume changes with age.
Hippocampus — A curved structure deep in the brain that plays a central role in forming new memories. Researchers often measure it on brain scans to look for shrinkage.
Leptin — A hormone made by fat tissue that is tied to appetite and energy balance.
Leucine — An essential amino acid, meaning your body can’t make it and it has to come from food. It is one of the building blocks of protein and is studied for its role in signaling muscle to build new protein.
Mitochondria — The parts of a cell that turn food into usable energy.
Bacteroides 2 enterotype — One gut microbiome type, defined by its mix of bacteria, in which the genus Bacteroides is prominent. In one large study covered on Bettering Me it was linked to higher inflammatory proteins and less favorable metabolic profiles. That is an association, not proof of cause.
Bone mineral density (BMD) — A measure of how much mineral, mainly calcium, is packed into a given area of bone. It is usually taken with a DEXA scan, and lower density means weaker bone.
Cortisol — A hormone made by the adrenal glands that rises in response to stress and follows a daily rhythm, highest in the morning and lowest at night.
Cytokine — A small signaling protein released by immune cells to coordinate the immune response. Some cytokines promote inflammation, and these are called pro-inflammatory.
Diastolic blood pressure — The lower of the two blood pressure numbers. It reflects the pressure in your arteries between heartbeats, when the heart relaxes and refills.
DNA methylation — Small chemical tags attached to DNA that can turn genes up or down without changing the DNA sequence itself. The pattern of tags shifts with age, which is what epigenetic clocks read.
DunedinPACE — An epigenetic measure of the pace of aging, built from DNA methylation in blood. It estimates how fast a person is aging biologically rather than how old their body looks.
Enterotype — A broad grouping of people by which bacteria dominate their gut microbiome. Enterotypes are one way researchers sort the wide variation in gut bacteria between people.
Epigenetic clock (epigenetic age) — A calculation that estimates biological age from patterns of DNA methylation, usually measured in blood. Epigenetic age acceleration means the clock reads older than the person’s calendar age.
Femoral neck — The narrow part of the thigh bone just below the ball of the hip joint. It is a standard site for bone density measurement and a common site of hip fractures.
GrimAge — An epigenetic clock designed to predict health outcomes and time to death from DNA methylation patterns in blood.
Hypertension — The medical term for persistently high blood pressure. Over time it strains the heart and blood vessels and raises the risk of heart attack, stroke and kidney disease.
Inflammaging (inflammaging-like) — A term for the low-grade, long-running inflammation that tends to rise with age, even without an infection.
Insulinogenic index — A measure of the early insulin response, calculated from how much insulin rises relative to glucose in the first 30 minutes of an oral glucose tolerance test.
Low bone mass (osteopenia) — Bone density lower than that of a typical healthy young adult, but not low enough to count as osteoporosis. Doctors call this range osteopenia.
Lumbar spine — The lower-back section of the spine. It is one of the standard sites where bone density is measured.
Matsuda index — A measure of whole-body insulin sensitivity, calculated from glucose and insulin levels during an oral glucose tolerance test. A higher value means the body responds to insulin more readily.
Microbiome diversity — How many different kinds of microbes live in your gut, and how evenly they are represented. It is often used as a rough summary of gut microbiome makeup.
Nocturnal dipping (dipping) — The normal drop in blood pressure that happens during sleep. When blood pressure falls less than expected overnight, doctors describe it as reduced dipping.
Osteoarthritis — A joint condition in which the cartilage that cushions the ends of the bones wears down over time, causing pain, stiffness and reduced movement. It is common in the knees, hips and hands.
Osteoporosis — A condition in which bones become thin and porous, so they break more easily. It is diagnosed with a bone density scan and is far more common after menopause.
PhenoAge — An epigenetic clock trained to track a blood-test-based estimate of biological age that is linked to mortality risk.
Stroke — Damage to part of the brain when its blood supply is blocked or a blood vessel in the brain bleeds. It can cause sudden weakness, speech trouble or loss of vision, and it is a medical emergency.
T-score — The number a bone density scan reports to compare your bone density with the average for healthy young adults. A score between −1.0 and −2.5 is generally classed as low bone mass (osteopenia), and a score below −2.5 as osteoporosis.
Hormone therapy (menopausal) — Medication that replaces some of the estrogen, and often a progestogen, that the body makes less of after menopause. It is mainly prescribed for symptoms such as hot flashes, and the decision depends on your age, health history and timing.
GLP-1 receptor agonist — A class of medication that mimics the gut hormone GLP-1. It slows stomach emptying, reduces appetite and helps the body release insulin when blood sugar is high. It is used for type 2 diabetes and for weight management.
Semaglutide — A GLP-1 receptor agonist taken by weekly injection (or daily pill in one form), sold under brand names including Ozempic and Wegovy. It is used for type 2 diabetes and for weight loss.
Tirzepatide — A weekly injectable medication that activates two gut hormone receptors, GLP-1 and GIP. It is sold under brand names including Mounjaro and Zepbound and is used for type 2 diabetes and weight loss.
HOMA-IR — Homeostatic Model Assessment of Insulin Resistance. A number calculated from fasting glucose and fasting insulin that estimates how well the body responds to insulin. Higher values suggest more insulin resistance. It is an estimate, not a direct measurement.
Progestogen — A hormone, or a drug that acts like one, that mimics progesterone. In menopausal hormone therapy it is usually added to estrogen for women who still have a uterus, to protect the uterine lining.
Somatic Resilience terms
Vagal tone — A measure of how responsive your vagus nerve is — the nerve most responsible for shifting your body out of “fight or flight” and into rest-and-digest mode. Higher vagal tone is generally associated with faster recovery from stress.
Vagus nerve — The main nerve of the parasympathetic “rest and digest” system. It runs from the brainstem to the heart, lungs and gut, and it is always active. Vagal tone describes how strongly it steers your heart.
HRV (heart rate variability) — The variation in time between consecutive heartbeats. Counterintuitively, more variability is the healthy sign — it reflects a nervous system that can flexibly shift between stress and recovery states rather than staying locked in one.
RMSSD — The root mean square of successive differences between heartbeats, a common way to summarize heart rate variability. It mainly reflects the activity of the vagus nerve, and many wearables report a version of it. Watch the weekly trend, not a single reading.
Orthosomnia — Anxiety about sleep caused by obsessively monitoring sleep-tracker data. The tracker becomes the source of the sleep problem it was meant to solve.
Cyclic sighing — A breathing pattern (a double inhale through the nose followed by a long exhale) studied as a fast way to shift the nervous system toward calm, distinct from generic “deep breathing.”
Box breathing — A paced breathing pattern with four equal phases: inhale, hold, exhale, hold, usually 4 seconds each. Sometimes called square breathing.
Downstate / Upstate — Site shorthand for your nervous system’s recovery mode (downstate) versus its activated, performance mode (upstate). The core Somatic Resilience thesis is that both states need to be deliberately engineered, not left to chance.
Interoception — Your sense of what’s going on inside your body: heartbeat, breathing, hunger, muscle tension. Body-awareness practices train it, and researchers are still working out how best to measure it.
Craniovertebral angle — A measurement of head posture: the angle between a horizontal line through the base of your neck and a line to your ear. A smaller angle means your head sits further forward.
REM sleep (rapid eye movement sleep) — The sleep stage when most vivid dreaming happens. Brain activity looks close to waking, the eyes dart back and forth, and most of the body’s muscles are temporarily switched off.
Deep sleep (slow-wave sleep) — The deepest stage of non-REM sleep, also called N3, marked by slow, large brain waves. It is the hardest stage to wake someone from.
Polysomnography — An overnight sleep study that records brain waves, eye movements, muscle activity, breathing, heart rhythm, and blood oxygen. It is the standard way to measure sleep stages and diagnose sleep disorders.
Obstructive sleep apnea (OSA) — A sleep disorder in which the airway repeatedly closes or narrows during sleep. Breathing pauses, blood oxygen dips, and sleep gets fragmented. It is common, often goes undiagnosed, and is confirmed with a sleep study.
Sleep Regularity Index (SRI) — A score from 0 to 100 for how consistent your sleep and wake times are from one day to the next. A higher score means a steadier schedule.
Circadian rhythm — Your body’s roughly 24-hour internal clock. It shapes when you feel alert or sleepy, and also smaller daily swings in body temperature, hormones and physical performance. Light, meal timing and regular routines help keep it steady.
CBT-I (cognitive behavioral therapy for insomnia) — A structured, time-limited program that treats insomnia by changing the habits and thoughts that keep it going, such as irregular sleep schedules, lying awake in bed and worry about sleep. Major clinical guidelines recommend it as the first treatment for chronic insomnia, ahead of sleep medication.
Sleep-onset latency — How long it takes you to fall asleep after you try to. A shorter time usually means falling asleep more easily, and sleep studies and wearables can measure it.
Sleep efficiency — The percentage of your time in bed that you spend asleep. If you lie in bed for 8 hours and sleep 7, your sleep efficiency is about 88%.
Insomnia Severity Index (ISI) — A short questionnaire that scores how much trouble you have falling or staying asleep, and how much it affects your days. Researchers and clinicians use it to track whether an insomnia treatment is working.
Locus coeruleus — A small brainstem region that helps set alertness and arousal. In mice, growth hormone makes its neurons more excitable and increases wakefulness.
Perceived stress — How overwhelmed, unpredictable or out of control your life feels, regardless of what’s objectively going on. It’s usually measured with the 10-question Perceived Stress Scale, which asks about the past month.
Circadian misalignment — A mismatch between your body’s internal 24-hour clock and your actual sleeping, eating and activity times, as happens with night work or jet lag. In lab studies, eating at night while the clock expects sleep worsens how the body handles blood sugar.
Actigraphy (actigraph) — A way to estimate sleep and waking from movement, using a wrist-worn motion sensor called an actigraph, usually worn for days or weeks. It is easier to use at home than a sleep lab, but it infers sleep from movement rather than measuring brain activity.
Adenosine — A chemical that builds up in the brain the longer you are awake, creating sleep pressure. Caffeine works mainly by blocking adenosine’s receptors.
Chronotype — Your natural tendency to be alert and sleepy earlier or later in the day. “Early” chronotypes feel best in the morning; “late” chronotypes naturally run later. It reflects your internal body clock and differs from person to person.
Electroencephalography (EEG) — A recording of the brain’s electrical activity, made with sensors on the scalp. It is the standard way to measure sleep stages and brain-wave patterns in sleep research.
Non-REM sleep — All the stages of sleep other than REM sleep, running from light sleep down into deep (slow-wave) sleep. Over a night, non-REM and REM sleep alternate in cycles.
Apnea-hypopnea index (AHI) — The number of breathing pauses (apneas) and shallow-breathing episodes (hypopneas) per hour of sleep. It is the standard score used to gauge how severe sleep apnea is, and higher numbers mean more severe.
High-intensity interval training (HIIT) — Exercise that alternates short bursts of hard effort with periods of easier effort or rest.
HiRIT (high-intensity resistance and impact training) — A supervised exercise program that combines heavy resistance lifting with impact movements such as jumping. Researchers have studied it in people with low bone mass.
Insomnia — Ongoing trouble falling asleep, staying asleep or waking too early, along with daytime problems such as tiredness or poor concentration. When it happens often and lasts for months, it is called chronic insomnia.
One-repetition maximum (1RM) — The heaviest weight you can lift for a single repetition of an exercise with good form. Strength training intensity is often described as a percentage of it.
Sleep deprivation — Not getting enough sleep, whether from staying awake through a night or a long stretch, or from repeated short nights.
Sleep pressure — The build-up of your body’s drive to sleep the longer you stay awake. It is highest after a long stretch awake and eases as you sleep.
Sleep-disordered breathing — An umbrella term for conditions in which breathing is repeatedly disrupted during sleep, from habitual snoring to obstructive sleep apnea.
Pittsburgh Sleep Quality Index (PSQI) — A questionnaire that asks about sleep over the past month, including how long it takes to fall asleep, how long you sleep and whether you use sleeping medication. Lower scores mean better sleep quality.
Epworth Sleepiness Scale — A short questionnaire that asks how likely you are to doze off in everyday situations, such as reading or watching television. Higher scores mean more daytime sleepiness.
SF-36 — A 36-question health survey in which people rate their own physical and mental well-being, including energy, pain, emotional health and daily functioning. It is a common way to measure quality of life.
Screen apnea (email apnea) — A term coined by writer Linda Stone for the habit of holding your breath or breathing shallowly while using a screen, especially while reading email. It comes from informal observation rather than controlled research, is not a medical diagnosis, and is different from sleep apnea.
Startle response — A fast, protective reflex to a sudden, intense stimulus such as a loud noise, run by a short circuit in the lower brainstem. Fear can increase its strength.
Polyvagal theory — A framework proposed by neuroscientist Stephen Porges holding that the autonomic nervous system shifts between states depending on perceived safety or threat. It is influential but debated, and is treated here as a lens rather than a settled mechanism.
Social jet lag — The gap between your sleep timing on workdays and on free days, such as sleeping in on weekends. It is called jet lag because the repeated shift resembles a small time-zone change.
Cognitive Sovereignty terms
Digital Sovereignty — Site-coined term for setting the terms of your relationship with technology deliberately, rather than defaulting to whatever a notification, feed, or app is optimized to make you do.
Attention residue — The cognitive trace left behind when you switch tasks, even briefly. It measurably degrades performance on whatever you turn to next — the underlying reason “just glancing” at a notification isn’t free.
Cognitive Sovereignty — The pillar name for treating focus as a finite, defendable resource rather than something that should be available to any app or notification that asks for it.
Bipolar spectrum — The range of mood conditions that involve episodes of elevated mood. Bipolar I includes at least one full manic episode; bipolar II includes milder hypomanic episodes plus major depressive episodes; subthreshold forms have symptoms that don’t meet the full criteria for either.
Default mode network — The set of brain regions that is most active when your mind wanders or you think about yourself, the past or the future. It is typically quieter during focused tasks. Many attention practices are studied for how they change its activity.
Neuroplasticity — The brain’s ability to change its connections and structure in response to repeated experience or practice. It is real but gradual, and studies comparing experienced practitioners with non-practitioners can’t show on their own that the practice caused the difference.
Trait mindfulness — How mindful you tend to be in everyday life, apart from any meditation practice. It’s usually measured with a questionnaire asking how often your mind wanders or you act on autopilot.
MMSE (Mini-Mental State Examination) — A short, widely used screening test of thinking skills such as orientation, memory, attention and language, scored out of 30. It can flag possible problems, but it is not a diagnosis.
MoCA (Montreal Cognitive Assessment) — A short screening test of thinking skills, scored out of 30, often used to check for mild cognitive impairment. Like the MMSE, it flags possible problems but is not a diagnosis.
Psychological flexibility — The ability to adjust your thoughts and actions when circumstances change, rather than getting stuck in one response. Researchers treat it as a skill that supports resilience, meaning how well you bounce back from stress.
Cognitive offloading — Using an outside tool, such as a phone, camera or notes, to hold information instead of relying on your own memory.
Hit rate — In a recognition memory test, the share of previously seen items that a person correctly says they have seen before.
Photo-taking impairment effect — The finding in some experiments that people who photograph an object or scene later remember fewer details about it than people who simply looked at it.
Recognition memory — The ability to tell that you have seen or heard something before when it is shown to you again, as opposed to recalling it from scratch.
Source memory — Memory for where, when or how you learned something, rather than just the information itself.
Vigilance decrement — The decline in performance on a long, monotonous task that requires sustained attention. It typically gets worse the longer you stay on the task without a change.
Mindfulness meditation — A practice of deliberately holding attention on present-moment experience, such as the breath, and noticing when the mind wanders. It is studied as a form of attention training, with evidence that is promising but still developing.
Cross-pillar terms
Vitality Span — Site-coined alternative to “lifespan” or “healthspan” — the stretch of years you’re not just alive, but capable of doing the things that make life worth extending in the first place.
Tactical Health Infrastructure — The site’s framing for its own content: not a single hack or supplement, but the small set of durable systems (sleep, strength, blood work, attention) that compound over years.
Implementation intention — An if-then plan that ties a specific action to a specific cue, such as “If the coffee is brewing, then I’ll do ten slow breaths.” Research finds it works better than a vague resolution.
Automaticity — How little effort or conscious thought a behavior takes. Habit researchers use it as the measure of whether something has become a habit.
Hazard ratio — A comparison of how often an event, such as a diagnosis or death, happens over time in one group versus another. A ratio of 1.0 means no difference, 0.74 means a 26% lower rate, and 1.25 means a 25% higher rate. On its own it shows an association, not a cause.
Comorbidity — Having two or more health conditions at the same time, such as ADHD and bipolar disorder. Comorbid conditions can share symptoms, which can make each one harder to recognize and diagnose.
Active control group — A comparison group in a trial that receives a real activity instead of nothing. It shows whether a new intervention beats a reasonable alternative, not just whether doing something beats doing nothing.
Fine-needle aspiration biopsy (FNAB) — A way to sample a lump, such as a thyroid nodule, with a very thin needle, usually in a clinic visit lasting minutes. Cells are drawn out and examined under a microscope to see whether the lump is benign or needs more follow-up.
Underpowered — A study with too few participants to reliably detect an effect of the size it’s looking for. An underpowered study can miss a real benefit, or show a small “win” that’s just luck. A result like this needs confirming in a larger trial.
Collaborative care — A care model where a care manager, often a nurse, helps you work through problems, supports self-management and coordinates with the rest of your care team, such as your doctor.
Guided self-help — A treatment you work through mostly on your own, from a book or online modules, while a professional checks in with feedback now and then. It takes far less clinician time than weekly therapy sessions.
Non-inferiority trial — A study design that asks whether a newer option is “not meaningfully worse” than the standard one, within a margin set in advance. Failing to show that isn’t the same as showing the newer option doesn’t work.
Ecological momentary assessment (EMA) — Short check-ins, usually on your phone, at random moments during ordinary days. They catch how you feel right now instead of relying on memory of the past week.
All-cause mortality — Death from any cause, as opposed to death from one specific disease. Researchers use it as a catch-all measure of whether a habit, such as eating more of a certain food, goes with living longer. It is usually reported as a hazard ratio, where a number below 1 means lower risk.
Systematic review — A study that gathers every available study on one question using a set search method, then judges and summarizes them together. It is stronger than any single study, but only as strong as the studies inside it.
Randomized controlled trial — A study that randomly assigns people to a treatment or to a placebo and then compares results. Because chance decides who gets what, it is the strongest design for showing that a treatment itself caused a change.
Cohort study (cohort) — A study that follows a group of people over time, recording their habits or exposures at the start and then which health outcomes follow. It can show that things go together, but not that one caused the other.
Confidence interval (CI) — A range of values that shows how precise a study’s estimate is. A 95% confidence interval is built so that, across many repeats of the study, about 95% of such ranges would contain the true value. A wide range means less certainty, and a range that includes “no difference” (1.0 for ratios, 0 for differences) means the result is not statistically clear.
Crossover trial (crossover) — A trial in which every participant goes through each of the conditions being compared, one after another, often with a gap called a washout in between. Each person is compared with themselves, which reduces the noise from differences between people.
Mediation (mediation analysis) — A statistical method that asks how much of one thing’s effect on another runs through a middle step. For example, how much of exercise’s effect on thinking skills travels through better sleep. It can suggest a pathway, but it can’t prove that the middle step is the cause.
MET-hour — A unit of exercise volume. One MET is the energy you use sitting at rest, and an activity rated at 4 METs uses about four times that. MET-hours multiply the rating by the hours spent, so different activities can be added into one weekly total.
Meta-analysis — A study that statistically pools the results of several earlier studies on the same question into one overall estimate. It is only as reliable as the studies that go into it.
Narrative review — A review that summarizes and discusses the research on a topic in words, without a fixed search method and without pooling the numbers. It is useful for context, but it is less rigorous than a systematic review.
Network meta-analysis — A meta-analysis that compares several treatments at once, including pairs that were never tested head to head, by linking trials through the treatments they share. The result is usually a ranking, and a rank is not the same as the size of the effect.
Observational study (observational) — A study that records what people do and what happens to them without assigning anyone to a treatment. It can show that two things go together, but it can’t prove that one caused the other, because other differences between people may explain the pattern.
Odds ratio (OR) — A way to compare how likely an outcome is in one group versus another. An odds ratio of 1 means no difference, above 1 means higher odds, and below 1 means lower odds.
Relative risk (absolute risk) — Relative risk compares the chance of an outcome between two groups, such as “15% lower.” Absolute risk is the actual chance for a person, such as 3 in 100 versus 2 in 100. When the starting risk is low, a large relative drop can be a small absolute change, so you need both to judge size.
Standardized mean difference (SMD) — A way to compare effects measured on different scales by expressing the difference between groups in standard-deviation units. By a common rule of thumb, around 0.2 is small, 0.5 is medium and 0.8 is large.
Cross-sectional study — A study that measures people at a single point in time. It can show that two things go together, but not which came first or whether one caused the other.
Food frequency questionnaire — A questionnaire that asks how often a person eats listed foods over a set period. It is inexpensive to use in large studies, but it relies on memory and self-report.
I-squared (I²) — A statistic in a meta-analysis that estimates how much of the variation in results between studies reflects real differences rather than chance. A higher percentage means the studies disagree more with each other (heterogeneity).
J-shaped relationship (J-shaped) — A pattern in which risk is lowest in the middle of a range and rises at both ends, so a graph of it looks like the letter J. It means that more or less is not always better.
Newcastle-Ottawa Scale — A checklist used to rate the quality of non-randomized studies. It scores how participants were selected, how comparable the groups were and how outcomes were measured.
Preregistered experiment — An experiment whose hypotheses and analysis plan were publicly recorded before any data were collected. This limits the chance of changing the analysis after seeing the results.
Standard deviation (SD) — A measure of how spread out values are around the average. Studies often express differences in standard-deviation units so results measured on different scales can be compared.
Umbrella review — A review that gathers existing systematic reviews and meta-analyses on a topic and summarizes them together. It is only as reliable as the reviews it includes.
Retrospective cohort study — A study that looks back at existing records for groups of people who were already treated differently, and compares what happened to them. Because nobody was assigned to a group, it can show associations but struggles to prove cause.
Confounding — When a third factor is tied to both the exposure and the outcome and distorts the apparent link between them. A confounder is the factor itself. Researchers adjust for known confounders statistically, but unmeasured ones can remain.
Secondary analysis — A new analysis of data that was already collected in an earlier study, often looking at different outcomes than the original question. Findings are usually less certain because the study was not designed around them.
Creatine — A compound your body makes and stores in muscle. Supplements raise those stores, and they are studied mainly for strength and lean mass when combined with resistance training.
Position stand — A formal statement from an expert society that reviews the evidence on a topic and sets out its official position. Check who funded it and what interests its authors declare.
Dysfunctional breathing — A breathing pattern that is too deep, too fast, or erratic, sometimes called hyperventilation syndrome. Its symptoms can include breathlessness, chest tightness, dizziness and tingling.
Lean mass — Body weight that is not fat, mostly muscle, water and bone. Often measured with a DXA scan, and sometimes reported for the arms and legs only.
Kinesiophobia — Fear of movement or of re-injury, often leading people to avoid activity. In back pain research it is commonly measured with the Tampa Scale of Kinesiophobia.
Nonspecific chronic low back pain — Back pain lasting months with no single identifiable structural cause, such as a fracture or a specific nerve problem.
Periodization — Planning training load to change in stages over time, rather than keeping it the same every session. The aim is steady, progressive adaptation.
Missing a term? This page gets updated as new posts introduce new vocabulary — check back, or follow the link from wherever you found the term.
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