Healthy Aging Glossary

The reduced sensitivity of aging muscle tissue to the anabolic (muscle-building) signals triggered by protein intake and exercise. Older adults require greater amounts of dietary protein -- particularly leucine -- and a stronger exercise stimulus to achieve the same muscle protein synthesis response as younger adults. This is a key reason why protein targets and training intensity both need to be higher after 40.

A protein that supports the survival, growth, and maintenance of neurons. BDNF is essential for hippocampal neurogenesis -- the creation of new neurons in the brain region most critical for memory. Levels decline with age. Aerobic exercise is one of the most potent known stimulators of BDNF production, operating through a lactate-driven pathway that activates its expression in the hippocampus. Low BDNF is associated with accelerated hippocampal atrophy and increased risk of depression.

A state in which a cell has permanently stopped dividing but remains metabolically active. Senescent cells accumulate throughout tissues with age. They secrete a mix of inflammatory signals called the senescence-associated secretory phenotype (SASP), which drives local tissue inflammation, disrupts neighboring cells, and contributes to the chronic low-grade inflammatory state known as inflammaging. Senescence plays protective roles in youth (wound healing, tumor suppression) but becomes harmful when cells accumulate faster than they are cleared.

The brain's waste clearance mechanism -- a network of channels that flush cerebrospinal fluid through brain tissue to remove metabolic byproducts, including amyloid-beta and tau protein. It operates primarily during slow-wave (deep) sleep. Glymphatic dysfunction is implicated in Alzheimer's disease pathology, as waste accumulates when the system is impaired or sleep is insufficient. Aerobic exercise and quality sleep are the two lifestyle inputs most strongly associated with healthy glymphatic function.

A blood biomarker that measures low-level systemic inflammation. CRP is produced by the liver in response to IL-6. The high-sensitivity assay detects the small elevations relevant to chronic inflammation rather than acute infection. Values below 1 mg/L are considered low risk; 1-3 mg/L is intermediate; above 3 mg/L is associated with significantly elevated cardiovascular and all-cause mortality risk. hs-CRP is one of the most accessible and clinically useful markers of inflammaging -- available on standard panels and generally covered by insurance.

A chronic, low-grade, sterile inflammatory state that develops and intensifies with age. Coined by researcher Claudio Franceschi in 2000. Unlike acute inflammation (which resolves), inflammaging is persistent, systemic, and driven by multiple sources including senescent cells (SASP), gut dysbiosis, visceral adipose tissue, and mitochondrial damage. Elevated inflammatory markers -- particularly IL-6, TNF-alpha, and hs-CRP -- characterize the condition. Inflammaging accelerates muscle loss, cardiovascular disease, cognitive decline, and virtually every other hallmark of aging.

The progressive, age-related loss of skeletal muscle mass, strength, and function. Sarcopenia begins as early as the 30s, accelerates after 60, and is a primary driver of frailty, falls, and functional decline in older adults. It is not inevitable -- resistance training and adequate protein intake are the two most evidence-supported interventions.

The maximum rate at which the body can consume oxygen during intense exercise. VO2 max is considered one of the strongest predictors of all-cause mortality and cardiovascular health. It declines approximately 10% per decade with age but responds well to aerobic training -- even in older adults. Higher VO2 max is associated with longer healthspan.