Alertness is a state of active attention characterized by high sensory awareness. Someone who is alert is vigilant and promptly meets danger or emergency, or is quick to perceive and act. Alertness is a psychological and physiological state.

Lack of alertness is a symptom of a number of conditions, including narcolepsy, attention deficit disorder, chronic fatigue syndrome, depression, Addison's disease, and sleep deprivation. Pronounced lack of alertness is an altered level of consciousness. States with low levels of alertness include drowsiness.

The word is formed from "alert", which comes from the Italian all'erta (on the watch, literally: on the height; 1618).[citation needed]

Wakefulness refers mainly to differences between the sleep and waking states; vigilance refers to sustained alertness and concentration. Both terms are sometimes used synonymously with alertness.

Importance and difficulty

Domenico Tintoretto, Allegory of Vigilance

People who have to be alert during their jobs, such as air traffic controllers or pilots, often face challenges maintaining their alertness. Research shows that for people "...engaged in attention-intensive and monotonous tasks, retaining a constant level of alertness is rare if not impossible." If people employed in safety-related or transportation jobs have lapses in alertness, this "may lead to severe consequences in occupations ranging from air traffic control to monitoring of nuclear power plants."[1]

Neurobiological pathways

See also: Stimulant § Mechanisms of action, and Neuroenhancement

Neurotransmitters that can initiate, promote, or enhance wakefulness or alertness include serotonin, (nor)epinephrine, dopamine (e.g. blockade of dopamine reuptake), glutamate, histamine, and acetylcholine. Neuromodulators that can do so include the neuropeptide orexin. Similarly inhibition or reduction of mechanisms causing sleepiness, or drowsiness such as certain cytokines and adenosine (as with caffeine) may also increase perceived wakefulness and thus alertness.[ambiguous][2][3][4]

Wakefulness depends on the coordinated effort of multiple brain areas. These are affected by neurotransmitters and other factors.[3] Many Neurotransmitters are in effect to experience wakefulness to include GABA, Acetylcholine, Adenosine, Serotonin, Norepinephrine, Histamine, and Dopamine.[5] There is not an isolated neurotransmitter that alone is responsible for the sensation of wakefulness. However, it is known that many transmitters are used together to cause this effect.[5][6] Research to map the wakefulness circuitry is ongoing.[6]

Beta power has been used as an indicator of cortical arousal or alertness by several studies.[further explanation needed][7] A study also measured alertness with EEG data.[further explanation needed][8]

Additional information can be found on the neurobiology, neuroscience, brain, behavioral neuroscience, and neurotransmitter pages.

Drugs used to increase alertness

The stimulant and adenosine receptor antagonist caffeine is widely used to increase alertness or wakefulness and improve mood or performance. People typically self-administer it in the form of drinks like green tea (where it is present alongside the l-theanine), energy drinks (often containing sugar/sugar-substitutes), or coffee (which contains various polyphenols). The chemicals that accompany caffeine in these preparations can potentially alter the alertness-promoting effects of caffeine.[9] Caffeine is the world's most consumed stimulant drug.[10]

Various natural biochemicals and herbs may have similar anti-fatigue effects, such as rhodiola rosea.[11] Various psychostimulants like bromantane have also been investigated as potential treatments for conditions where fatigue is a primary symptom.[12] The alkaloids theacrine and methylliberine are structurally similar to caffeine and preliminary research supports their pro-alertness effects.[13]

During the Second World War, U.S. soldiers and aviators were given benzedrine, an amphetamine drug, to increase their alertness during long periods on duty. While air force pilots[where?] are able to use the drug to remain awake during combat flights, the use of amphetamines by commercial airline pilots is forbidden.[where?][citation needed] British troops used 72 million amphetamine tablets in the second world war[14] and the Royal Air Force used so many that "Methedrine won the Battle of Britain" according to one report.[15][attribution needed] American bomber pilots used amphetamines ("go pills") to stay awake during long missions. The Tarnak Farm incident, in which an American F-16 pilot killed several friendly Canadian soldiers on the ground, was blamed by the pilot on his use of amphetamine. A nonjudicial hearing rejected the pilot's claim.

Amphetamine is a common study aid among college and high-school students.[16] Amphetamine increases energy levels, concentration, and motivation, allowing students to study for an extended period of time.[citation needed] These drugs are often acquired through diverted prescriptions of medication used to treat ADHD, acquired from fellow students, rather than illicitly produced drugs.[17] Cocaine is also used to increase alertness,[18] and is present in coca tea.[19]

The eugeroic modafinil has recently gained popularity with the US Military[20][vague] and other militaries.

Other approaches for increasing alertness

Beyond good sleep, physical activity, and healthy diet, a review suggests odours, music, and extrinsic motivation may increase alertness or decrease mental fatigue.[21] Short rest periods and adjustments to lighting (level and type of) may also be useful.[22] Various types of neurostimulation are being researched,[23][further explanation needed] as is the microbiome and related interventions.[2]

Alertness after waking

A study suggests non-genetic determinants of alertness upon waking up from sleep are:[24][25]

The baseline of daily alertness[clarification needed] is related to the quality of their[clarification needed] sleep (currently[may be outdated as of July 2023] measured only by self-reported quality), positive emotional state (specifically self-report happiness), and age.[25] There are genes that enable people to be apparently healthy and alert with little sleep. However, twin-pair analyses indicate that the genetic contribution to daytime alertness is small.[25] Other factors such as natural light exposure[25] and synchronicity with the circadian rhythm may matter as well.

Behavioral ecology

Vigilance is important for animals so that they may watch out for predators. Typically a reduction in alertness is observed in animals that live in larger groups. Studies on vigilance have been conducted on various animals including the scaly-breasted munia.[27]

See also


  1. ^ Jung, Tzyy-Ping (17 November 1995). "Alertness Monitoring". The Salk Institute. Archived from the original on 2022-09-30.
  2. ^ a b Haarhuis, J.E.; Kardinaal, A.; Kortman, G.A.M. (3 August 2022). "Probiotics, prebiotics and postbiotics for better sleep quality: a narrative review". Beneficial Microbes. 13 (3): 169–182. doi:10.3920/BM2021.0122. PMID 35815493. S2CID 250423761.
  3. ^ a b Miller, Diane B.; O'Callaghan, James P. (October 2006). "The pharmacology of wakefulness". Metabolism. 55 (10 Suppl 2): S13–S19. doi:10.1016/j.metabol.2006.07.007. PMID 16979420.
  4. ^ Sakurai, Takeshi (August 2005). "Roles of orexin/hypocretin in regulation of sleep/wakefulness and energy homeostasis". Sleep Medicine Reviews. 9 (4): 231–241. doi:10.1016/j.smrv.2004.07.007. PMID 15961331.
  5. ^ a b Watson, Christopher J.; Baghdoyan, Helen A.; Lydic, Ralph (December 2010). "Neuropharmacology of Sleep and Wakefulness". Sleep Medicine Clinics. 5 (4): 513–528. doi:10.1016/j.jsmc.2010.08.003. ISSN 1556-4088. PMC 3026477. PMID 21278831.
  6. ^ a b Grady, Fillan S.; Boes, Aaron D.; Geerling, Joel C. (2022). "A Century Searching for the Neurons Necessary for Wakefulness". Frontiers in Neuroscience. 16: 930514. doi:10.3389/fnins.2022.930514. ISSN 1662-4548. PMC 9344068. PMID 35928009.
  7. ^ Küssner, Mats B. (2017). "Eysenck's Theory of Personality and the Role of Background Music in Cognitive Task Performance: A Mini-Review of Conflicting Findings and a New Perspective". Frontiers in Psychology. 8: 1991. doi:10.3389/fpsyg.2017.01991. ISSN 1664-1078. PMC 5694457. PMID 29184523.
  8. ^ Jagannathan, Sridhar R.; Ezquerro-Nassar, Alejandro; Jachs, Barbara; Pustovaya, Olga V.; Bareham, Corinne A.; Bekinschtein, Tristan A. (August 2018). "Tracking wakefulness as it fades: Micro-measures of alertness". NeuroImage. 176: 138–151. doi:10.1016/j.neuroimage.2018.04.046. PMID 29698731. S2CID 13680412.
  9. ^
  10. ^
  11. ^
  12. ^ Gill, G (1 January 2017). "Performance-Enhancing Drugs: A Review". UNM Orthopaedic Research Journal. 6 (1). ISSN 2167-4760.
  13. ^ Sheng, Yue-Yue; Xiang, Jing; Wang, Ze-Shi; Jin, Jing; Wang, Ying-Qi; Li, Qing-Sheng; Li, Da; Fang, Zhou-Tao; Lu, Jian-Liang; Ye, Jian-Hui; Liang, Yue-Rong; Zheng, Xin-Qiang (2020). "Theacrine From Camellia kucha and Its Health Beneficial Effects". Frontiers in Nutrition. 7: 596823. doi:10.3389/fnut.2020.596823. ISSN 2296-861X. PMC 7773691. PMID 33392238.
  14. ^ Mondenard De Monie, Jean-Pierre (2000). Dopage: l'imposture des performances: mensonges et vérités sur l'école de la triche. Chiron éd. ISBN 978-2-7027-0639-8. OCLC 997463239.
  15. ^ Grant, D.N.W.; Air Force, UK, 1944
  16. ^ Twohey, Megan (2006-03-25). "Pills become an addictive study aid". JS Online. Archived from the original on 2007-08-15. Retrieved 2007-12-02.
  17. ^ The Illicit Market for ADHD Prescription Drugs in Queensland (PDF). Queensland Crime and Misconduct Commission. April 2002. Archived from the original (PDF) on 2009-05-15. Retrieved 2008-01-13.
  18. ^ "Cocaine use rising among Hawaii workers, job applicants, lab says". Pacific Business News. 4 July 2014.
  19. ^ Chen, Cheng; Lin, Ligen (2019). "Alkaloids in Diet". Handbook of Dietary Phytochemicals. Springer. pp. 1–35. doi:10.1007/978-981-13-1745-3_36-1. ISBN 978-981-13-1745-3. S2CID 214115630.
  20. ^ "Defense Technical Information Center Compilation Part Notice ADPO 11050" (PDF). Defense Technical Information Center. Archived (PDF) from the original on March 4, 2016.
  21. ^ Proost, Matthias; Habay, Jelle; De Wachter, Jonas; De Pauw, Kevin; Rattray, Ben; Meeusen, Romain; Roelands, Bart; Van Cutsem, Jeroen (September 2022). "How to Tackle Mental Fatigue: A Systematic Review of Potential Countermeasures and Their Underlying Mechanisms". Sports Medicine. 52 (9): 2129–2158. doi:10.1007/s40279-022-01678-z. PMID 35543922. S2CID 248672972.
  22. ^ Bonnefond, Anne; Tassi, Patricia; Roge, Joceline; Muzet, Alain (2004). "A Critical Review of Techniques Aiming at Enhancing and Sustaining Worker's Alertness during the Night Shift". Industrial Health. 42 (1): 1–14. doi:10.2486/indhealth.42.1. PMID 14964612.
  23. ^ Bagary, Manny (2011). "Epilepsy, Consciousness and Neurostimulation". Behavioural Neurology. 24 (1): 75–81. doi:10.3233/BEN-2011-0319. PMC 5377955. PMID 21447901.
  24. ^ "What are the factors that affect how alert we feel in the morning?". 29 November 2022. Retrieved 13 December 2022.
  25. ^ a b c d Vallat, Raphael; Berry, Sarah E.; Tsereteli, Neli; Capdevila, Joan; Khatib, Haya Al; Valdes, Ana M.; Delahanty, Linda M.; Drew, David A.; Chan, Andrew T.; Wolf, Jonathan; Franks, Paul W.; Spector, Tim D.; Walker, Matthew P. (19 November 2022). "How people wake up is associated with previous night's sleep together with physical activity and food intake". Nature Communications. 13 (1): 7116. Bibcode:2022NatCo..13.7116V. doi:10.1038/s41467-022-34503-2. ISSN 2041-1723. PMC 9675783. PMID 36402781.
  26. ^
  27. ^ Roche, Erin A.; Brown, Charles R. (December 2013). "Among-individual variation in vigilance at the nest in colonial Cliff Swallows". The Wilson Journal of Ornithology. 125 (4): 685–695. doi:10.1676/12-196.1. ISSN 1559-4491. S2CID 13865609.