Cognition

BDNF is a growth-factor protein that supports neuronal survival, synapse formation, and — at least in animal models — adult hippocampal neurogenesis (its extent in adult humans remains debated). Levels rise with aerobic exercise and quality sleep; effects of intermittent fasting are well-established in rodents but less clear in humans, and levels fall under chronic stress and depression. In longevity research, lower BDNF is associated with depression and Alzheimer's risk, linking lifestyle to memory and mood regulation.

Cognitive reserve, developed and formalised by Yaakov Stern building on earlier brain-reserve work (Katzman and colleagues, late 1980s), refers to the brain's functional adaptability — built through education, complex work, multilingualism, and lifelong learning. It is distinguished from brain reserve, the structural or biological capacity often operationalised via measures of brain integrity and size. Higher cognitive reserve is associated with better cognitive outcomes for a given level of pathology. In longevity science, it is a central modifiable target of brain-health interventions, helping postpone dementia symptoms.

Flow, described by psychologist Mihaly Csikszentmihalyi, is a state of deep absorption in a challenging activity matched to one's skill, accompanied by reduced self-awareness and altered time perception. It is a popular wellbeing concept whose subjective experience is well-documented, while neural correlates remain debated. For longevity it is relevant because regular flow correlates with life satisfaction, sustained engagement, and the kind of meaningful activity that supports cognitive aging.

Hippocampal volume measures the size of the brain region central to memory consolidation and spatial navigation. Atrophy rates vary by cohort and method: Jack et al. report roughly 1.55 percent per year in cognitively normal controls, accelerating to about 3.98 percent per year in Alzheimer's disease. MRI-derived volume serves as an early biomarker of cognitive aging. Aerobic exercise has been shown to preserve or even enlarge it (Erickson et al. 2011, PNAS), while separate lines of evidence link sleep quality and chronic stress to hippocampal structure.

Ikigai is a Japanese concept loosely translated as a sense of purpose or reason for being, encompassing everyday sources of meaning — relationships, routines, small pleasures — as described by Japanese scholars such as Mieko Kamiya. The popular four-circle Venn diagram (what you love / are good at / can be paid for / what the world needs) is not Japanese in origin: it was created by blogger Marc Winn in 2014 by relabeling Andrés Zuzunaga's unrelated 2011 Spanish purpose diagram, and has no documented connection to Okinawa. The underlying construct of life purpose has been linked in observational studies (e.g., Sone et al. 2008, Ohsaki cohort) to lower cardiovascular mortality.

Loneliness, the subjective feeling of social disconnection, is now recognised as an independent risk factor for cardiovascular disease, dementia, and early mortality. Meta-analyses by Holt-Lunstad and colleagues (2010, 2015) found social isolation and loneliness raise all-cause mortality risk by roughly 26 to 32 percent — an effect she has compared by analogy to smoking up to 15 cigarettes a day. It dysregulates inflammation, sleep, and HPA-axis stress responses. In longevity science, addressing loneliness through community, purpose, and relationships is a primary, evidence-based intervention.

Defined by Petersen's diagnostic criteria (objective cognitive decline on testing, preserved daily functioning, not meeting dementia threshold), mild cognitive impairment exceeds normal aging without impairing independence. Roughly 10 to 15 percent of people with MCI progress to dementia each year in clinic-based cohorts, with lower rates in community samples. In longevity medicine it is a critical intervention window: lifestyle changes, treatment of vascular risk, sleep optimisation, and hearing correction can stabilise or partially reverse symptoms.

Mindfulness is the trained practice of bringing non-judgmental attention to present-moment experience, typically through meditation. Randomised trials show modest but consistent benefits for stress, anxiety, depression, chronic pain, and blood pressure. Some studies have linked long-term mindfulness practice to longer leukocyte telomeres and modestly reduced inflammatory markers, though findings are inconsistent and effect sizes are small. It remains a low-risk adjunct to standard brain-health and cardiometabolic interventions.

Neuroplasticity is the brain's lifelong capacity to reorganise its structure and synaptic connections in response to learning, experience, and injury. It underpins memory formation, recovery from stroke, and skill acquisition at any age. For longevity, neuroplasticity is the mechanism by which exercise, novel learning, social engagement, and sleep protect cognitive function and slow age-related decline.

Polyvagal theory, proposed by Stephen Porges in 1994, posits that distinct vagal branches — a phylogenetically newer ventral-vagal complex and an older dorsal vagal pathway — evolved in mammals to support social engagement versus shutdown/freeze responses. It is widely used in trauma therapy and somatic practice, but its comparative-neuroanatomy and evolutionary claims have been substantively challenged in peer-reviewed work (Grossman & Taylor 2007; Grossman 2023), and mainstream neuroscience does not treat it as established. The well-supported finding that vagal tone (HRV) and breathing influence health does not depend on polyvagal theory and should not be conflated with it.