Effects of Alcohol on the Human Body


This article aims to outline several symptoms of alcohol use and link them to flight safety.
It is recommended that you read this article first.

Alcohol is a Depressant

Basically what this means is that alcohol deprives the central nervous system. This causes impaired brain and body functioning which can be detected as early as 20mg/100ml BAC, further deterioration of functioning will occur as more alcohol is consumed (Hawkins, 1993[1]). Common symptoms of this effect are relaxation, lack of alertness, speech impairment, and lack of muscular coordination (Campbell & Bagshaw, 2002[2]).

Alcohol induced Acidosis

This is a form of metabolic acidosis which means it happens because of something you have ingested. Alcohol causes an excessive production of lactic acid within our body, of which our kidneys cannot always remove quick enough, and this will cause rapid breathing, confusion, and if severe enough can lead to shock or death (National Library of Medicine, 2011a[3]). The worrying thing about this effect is that it can occur many hours after alcohol is ingested, to the point where a pilot may be legal to fly but then suffers from these symptoms, potentially causing an accident.

Alcohol induced Ketoacidosis

Chronic alcoholics may develop ketoacidosis if they suddenly stop drinking and they have poor nutrition (Fauci et al., 2008[4]). Ketoacidosis is when your body burns fat instead of sugar because not enough insulin is being produced to convert the glucose into energy. By breaking down fat we produce ketoacids, excessive amounts of these can cause symptoms such as nausea, and hypoglycaemia (low blood sugar) (Ansstas, Robinson, Rubinchik, & Schade, 2011[5]). Once again these symptoms could occur long enough after drinking to be legal to fly. Nausea and low blood sugar will affect concentration and cognitive abilities of pilots (or humans in general) so this is a risk in the aviation context. Upper gastrointestinal haemorrhage (internal bleeding from stomach or intestines), pancreatitis (inflammation of the pancreas, an organ that produces insulin), and pneumonia (inflammation of the lungs) may also complicate this disorder (Fauci et al., 2008[4]).

Alcohol induced Hypoglycaemia

This is often linked with the earlier discussed Ketoacidosis. It is prevalent in people who have diabetes, or healthy people who have been fasting (even more serious if both). Hypoglycaemia is having low blood sugar. Symptoms start with the impairment of short-term memory, then inability to follow simple commands, and eventually leads to coma if untreated (Fauci et al., 2008[4]). Hypoglycaemia may take some time to take affect as it is the metabolism of alcohol that causes it, this means that you may be legal to fly, however still encounter this problem. As you can imagine, given the interaction between short term memory and information processing, even mild hypoglycaemia can impair performance in a cockpit situation.

Alcohol induced Nystagmus

Nystagmus is used to refer to rapid, involuntary movement of the eyes (National Library of Medicine, 2012[6]). Alcohol induces nystagmus during angular accelerations (ie turning) which reduces visual perception, particularly of things inside the cockpit (Watson, 1997[7]). With lack of visual cues it is not hard to see how this might cause or contribute towards an accident.

Positional Alcohol Nystagmus

This is caused by the occulovestibular (between eyes and balance) interaction. Our vestibular system provides us with our sense of balance. Alcohol can cause our vestibular system to work differently to how it is meant to. This is called positional alcohol nystagmus (PAN). In our vestibular system we have semi-circular canals filled with liquid, and this liquid passes through hairs with a weight on top of them. As the liquid flows it tilts these hairs in a certain direction and this shows our brain the direction of motion. Alcohol changes the density of the liquid in these semi-circular canals, making the weight on top of the hairs heavier. This means that when per se flying a turn, it will feel like we are turning more than what we actually are due to positional alcohol nystagmus. This problem can be further exacerbated by excess G forces. There has been several accidents attributed to this, one of which was a crash that happened during a low turn over Hamilton Island, Australia. The pilot assumed the duty of flying an aircraft 8.5hours after drinking (just legal). It was believed by the investigating authority that the pilot may have been suffering from vestibular dysfunction due to PAN, and this is why he crashed in good flying conditions during a routine low turn onto finals (Australian Transport Safety Bureau, 2004[8]).

Alcohol induced Sleep Deprivation

Alcohol deprives REM (rapid eye movement) sleep (Robson, 2008[9]). REM sleep is an essential form of sleep where we dream and consolidate memories (store in long-term memory) (Anderson, 2005[10]). The consequence of this deprivation is that we have all of our REM sleep towards the time we wake up. REM is also the most restless form of sleep (Robson, 2008[9]). This means we wake up out of REM sleep and will feel like we have had a poor sleep. We will also most likely be experiencing the effects of sleep inertia (a transitional state between sleep and wakefulness that has been shown to impair performance) (De Landre, Boag & Fletcher, 2003[11]).

Alcohol induced Gastritis

Alcohol can cause irritation of the stomach by inflaming the stomach lining (University of Maryland Medical Center, 2011[12]). Other symptoms may also pursue such as nausea, heartburn, and indigestion. Gastritis can last for days and may be complicated by ulceration and bleeding which can be sudden and severe. Alcohol is a very common cause of haemorrhagic gastritis (the ulceration and bleeding just mentioned) (Fauci et al., 2008[4]). Due to the rapid onset and severity of this it is a risk long after the legalities have been met. As you can imagine a gastric haemorrhage in flight would almost certainly cause an accident, and the pain caused by gastritis would certainly impair performance.

Alcohol induced Cardiac Dysrhythmia (Holiday Heart)

Short-term alcohol consumption can cause a problem commonly referred to as holiday heart. It is most common as supraventricular tachyarrhythmias (abnormally fast heart beat originating in the atrial part of the heart) in healthy people (Budzikowsky, Daubert, Smith, & Weiss, 2012[13]). There is a very minute risk of death associated with this syndrome in patients with underlying health conditions. Susceptibility to this may be influenced by genetics and it often occurs after a binge drink to people with no other evidence of heart disease (Fauci et al., 2008[4]). Holiday heart, once started usually takes 24 hours to resume normal rhythms (Thornton as cited in Budzikowsky, Daubert, Smith, & Weiss, 2012[13]). As this may extend into legal flying limits after alcohol, the best advice for pilots is don't risk it, especially if they feel unusual heart palpitations.

Alcohol and Mental Health Disorders

It has been shown in a study by Lai, Sitharthan, & Huang (2012[14]), that alcohol can be linked to several mental disorders. In fact during their study of inpatients in New South Wales hospitals, they found that 33.8% of patients that used alcohol regularly had at least 1 mental health disorder. Alcohol can be linked to increased rates of anxiety disorders, bipolar affective disorders, major depressive disorders, personality disorders, schizophrenia, and severe stress disorders (Lai, Sitharthan, & Huang, 2012[14]). Most of these will result in permanent disqualification from flying, although less serious ones may be disregarded after treatment (Green, Muir, James, Gradwell, & Green, 1996[15]). Is it really worth the risk?

Alcohol induced Impulsiveness

Alcohol removes inhibitions and anxiety (Robson, 2008[9]), to put it simply this means that you are more likely to do stupid things under the influence of alcohol. An example is that many suicide attempts are performed under the influence of alcohol. This is substantiated by Boenisch et al. (2010[16]) who found that 32% of suicide attempts happened after drinking alcohol. This is a drastic example, however, aircraft have been known for use in sabotage and suicide. Although these are unlikely, it goes to show the risk-taking and impulsiveness alcohol generates. Even small risks in the cockpit can lead to undesired aircraft states, and potentially accidents or incidents.

Alcohol induced Cirrhosis

Cirrhosis is basically when your liver does not perform as well as it should (National Library of Medicine, 2011b[17]). This can be caused by long-term alcohol abuse. This should not be of concern to most aviation professionals, unless they have an alcohol problem.


A hangover is one of the consequences of over-indulging on alcohol. This can cause fatigue and impair performance. A study by Yesavage & Leirer (1986[18]) compared navy pilot performances in a test environment. First, they simulated a flight at least 48hours since each pilot had finished drinking and measured their performance. Second, they measured the various pilots' performances 14 hours after reaching a BAC of 100mg/100ml (meaning the pilots were hung over). All the pilots tested consistently performed worse with a hangover than when they had been sober for 48 hours. It must be noted, however, that this will depend on the complexity of the tasks the pilot has to complete whilst suffering from this. When only dealing with simple tasks it is unlikely to impair performance, especially if the tasks are well learned (Cook, 1997[19]). However, it is still a possibility and should be avoided. This means that pilots should avoid flying with a hangover, even though they may meet the legal requirements to fly.

Alcohol and Altitude Tolerance

Alcohol has similar effects as does hypoxia on the human body, and therefore decreases our tolerance of altitude (Green et al., 1996[15]). Alcohol impairs the brain's ability to use available oxygen, which further impairs performance in terms of reasoning, memory and judgement when we are exposed to higher altitudes with less oxygen in the air (Salazar & Antuñano, n.d.[20]).


Alcoholism can be defined as engaging in behaviour where excessive use of alcohol damages a person's physical, mental, or social life (Green et al., 1996[15]). Robson (2008[9]) suggests that this should be extended to professional life as well. The World Health Organisation (2012[21]) states that the use of alcohol can impact negatively on people around us, and that alcoholism can be easily associated with absenteeism in the workplace. Both of these should be of concern to aviation managers, as our industry so readily relies on people being on time and getting things done cooperatively. Alcoholism should not be tolerated in any aviation professions, as it can put people in danger in many regards. Alcoholism can also cause dementia, psychiatric problems such as psychosis, vitamin deficiencies, cardiomyopathy (sudden death), and other health problems such as cerebellar problems (Fauci et al., 2008[4]). Essentially, there are so many problems that alcoholism causes it is hard to even scrape the surface in a concise manner. Alcoholism has the potential to hurt people, and should not be tolerated any walk of life.
McFadden & Towell (1999[22]) noted an interesting correlation between pilots who had had driving-under-influence (DUI) convictions and pilot-error accidents and incidents. Pilots were twice as likely to be involved in a pilot-error accident if they had received one DUI. Pilots were four times as likely to have an accident if they had had two or more DUIs. The exact reason for this is unclear however it may be due to certain personality traits such as poor judgment.

Alcohol dependence vs. Alcohol abuse

These two terms both relate back to alcoholism. The difference is that alcohol dependence involves repeated alcohol-related impairments in at least 3 areas of functioning, whereas alcohol abuse is repetitive problems with alcohol related to either social, interpersonal, legal, or occupational areas; or repeated use of alcohol in dangerous situations (eg flying intoxicated) (Fauci et al., 2008[4]). In simpler terms, alcohol dependence and alcohol abuse cause similar harmful effects, except for the fact that alcohol dependence requires addiction, whereas alcohol abuse can occur even in non-alcoholics. Once the brain has been exposed to high amounts of alcohol for so long, it is impossible to suddenly stop without producing withdrawal symptoms (Fauci et al., 2008[4]). Delirium tremens is an extreme state of mental confusion and agitation that although uncommon can be brought about by suddenly stopping alcohol intake (Fauci et al., 2008[4]). Also, if you are addicted to alcohol, you will have a higher tolerance for it, and will need more to get the same effect. Just to reiterate, both alcohol dependence and alcohol abuse have similar detrimental effects, however alcohol dependence requires an addiction, alcohol abuse can happen in alcoholics and non-alcoholics alike.


Given this broad analysis on the effects of alcohol on the human body it should not be too hard to see why alcohol should be avoided for aviation professionals. Alcohol can have many negative effects on the human body, and these when combined with a flightdeck scenario have the potential to cause great harm. This analysis should also bring home the real truth that legal requirements are not always a guarantee of safety. Many of the conditions can have sudden onsets long after meeting legal requirements to fly, and even hangovers and sleep deprivation have the potential to significantly impair performance. Thus it is the pilot's duty to educate him/herself on the effects of alcohol, and if unsure, prevent themselves from entering the cockpit, whether legal or not.

1. Hawkins, F.H. (1993). Human factors in flight (2nd ed.). Farnham, England: Ashgate.
2. Campbell, R.D. & Bagshaw, M. (2002). Human performance and limitations in aviation (2nd ed.). Oxford, United Kingdom: Blackwell Science.
3. National Library of Medicine. (2011a). Metabolic acidosis. Retrieved from http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001376/
4. Fauci, A.S., Braunwald, E., Kasper, D.L., Hauser, S.L., Longo, D.L., Jameson, J.L., & Loscalzo, J. (2008). Harrison's principles of internal medicine (17th ed.). New York, NY: McGraw Hill.
5. Ansstas, G., Robinson, I., Rubinchik, S.M., & Schade D.S. (2011). Alcoholic ketoacidosis. Retrieved from http://emedicine.medscape.com/article/116820-overview#showall
6. National Library of Medicine. (2012). Nystagmus. Retrieved from http://www.nlm.nih.gov/medlineplus/ency/article/003037.htm
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9. Robson, D. (2008). Human being pilot: Human factors for aviation professionals. Cheltenham, Australia: Aviation Theory Centre.
10. Anderson, H. (2005). Fatigue and sleep factors for shiftworkers. Christchurch, New Zealand: Caxton Press.
11. De Landre, J., Boag, C., & Fletcher, A. (2003, May/June). Asleep at the controls: Pilots and other shift workers, unaware of the effects of sleep inertia and microsleeps, may be putting lives at risk. Vector, (3), 8-11.
12. University of Maryland Medical Centre. (2011). Gastritis. Retrieved from http://www.umm.edu/altmed/articles/gastritis-000067.htm
13. Budzikowsky, A.S., Daubert, J.P., Smith, R.H., & Weiss, H.S. (2012). Holiday heart syndrome. Retrieved from http://emedicine.medscape.com/article/155050-overview#showall
14. Lai, H.M.X., Sitharthan, T., Huang, Q.R. (2012). Exploration of the comorbidity of alcohol use disorders and mental health disorders among inpatients presenting to all hospitals in New South Wales, Australia. Substance abuse, 33, 138-145.
15. Green, R.G., Muir, H., James, M., Gradwell, D., & Green, R.L. (1996). Human factors for pilots (2nd ed.). Farnham, England: Ashgate.
16. Boenisch, S., Bramesfeld, A., Mergl, R., Havers, I., Althaus, D., Lehfeld, H., … Hegerl, U. (2010). The role of alcohol use disorder and alcohol consumption in suicide attempts: A secondary analysis of 1921 suicide attempts. European Psychiatry, 25, 414-420.
17. National Library of Medicine. (2011b). Cirrhosis. Retrieved from http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001301/
18. Yesavage, J.A., & Leirer, V.O. (1986). Hangover effects of aircraft pilots 14 hours after alcohol ingestion: a preliminary report. American Journal of Psychiatry, 143(12), 1546-1550.
19. Cook, C.C.H. (1997). Alcohol and aviation. Addiction, 92(5), 539-555.
20. Salazar, G.J., & Antuñano, M.J. (n.d.) Alcohol and flying: A deadly combination. Oklahoma City, OK: Federal Aviation Administration. Retrieved from http://www.faa.gov/pilots/safety/pilotsafetybrochures/media/alcohol.pdf
21. World Health Organisation. (2012). Management of substance abuse: Alcohol. Retrieved from http://www.who.int/substance_abuse/facts/alcohol/en/index.html
22. McFadden, K. L., & Towell, E. R. (1999). Aviation human factors: a framework for the new millennium. Journal of Air Transport Management, 1999(5), 177-184.

Want to know more?

Alcohol in Aviation
For a more brief summary on the effects of alcohol it is recommended that you go to this link. It will also give you an overview of the prevalence of alcohol use in general aviation.

Contributors to this page

Authors / Editors

Isaac Levi HendersonIsaac Levi Henderson

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