# Caffeine

Caffeine is a methylxanthine alkaloid, found in coffee, tea, and cocoa. It works by blocking your adenosine A1 and A2A receptors. Normally, adenosine signaling makes you drowsy and quiets your neurons; caffeine competes with it and blocks that. With those receptors blocked, your brain releases more dopamine, glutamate, and acetylcholine. The result: more alertness, faster reactions, and steadier attention. Caffeine's half-life averages 5 to 6 hours in healthy adults. But it lengthens with age, liver problems, or oral contraceptives. So a late-afternoon dose can suppress your deep (slow-wave) and REM sleep. Habitual coffee drinking is linked to lower all-cause death. The NIH-AARP Diet and Health Study (Freedman et al. 2012, about 400,000 people) found 4 to 5 cups a day tied to hazard ratios of about 0.88 in men and 0.84 in women. The lower risk spanned heart, respiratory, stroke, diabetes, and infection causes. A meta-analysis of 23 studies (Malerba et al. 2013) backed an inverse trend at moderate intake. A2A blockade is also linked to lower Parkinson's risk in prospective data, and it underlies the approved drug istradefylline. But caffeine is neither approved as a therapy nor proven to protect causally; lifestyle confounding cannot be ruled out. A 2025 narrative review (Carbone et al.) notes that moderate intake may support alertness and offer some neuroprotection in aging, while too much can cause anxiety, sleep problems, and worse thinking or movement in older adults.

## Sources

- Freedman ND, Park Y, Abnet CC, Hollenbeck AR, Sinha R. (2012). Association of Coffee Drinking with Total and Cause-Specific Mortality. New England Journal of Medicine. https://doi.org/10.1056/NEJMoa1112010
- Malerba S, Turati F, Galeone C, Pelucchi C, Verga F, La Vecchia C, Tavani A. (2013). A meta-analysis of prospective studies of coffee consumption and mortality for all causes, cancers and cardiovascular diseases. European Journal of Epidemiology. https://doi.org/10.1007/s10654-013-9834-7
- Carbone MG, Pagni G, Tagliarini C, Maremmani I, Maremmani AGI. (2025). Caffeine in Aging Brains: Cognitive Enhancement, Neurodegeneration, and Emerging Concerns About Addiction. International Journal of Environmental Research and Public Health. https://doi.org/10.3390/ijerph22081171

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_Canonical: https://longevity-switzerland.com/en/glossary/caffeine · Part of Longevity Cities · Updated 2026-06-22_