The effects of alcohol on health, short and long term

Alcohol has a measurable impact on health on two very different time scales. It acts immediately, with every episode of heavy drinking, and progressively, as regular consumption sets in over time.

To understand these two scales, it helps to know what happens to alcohol in the body. It enters the bloodstream within minutes, mostly through the small intestine, then spreads to every organ, including the brain. The liver removes it at a roughly fixed rate, around 0.10 to 0.15 g/L of blood per hour. No coffee, no cold shower, and no physical exercise can speed up this process. To eliminate alcohol, the liver first turns it into acetaldehyde, a toxic substance that explains much of its long-term effects.

Short-term effects

From a single episode of heavy drinking, alcohol impairs judgment and decision-making and encourages risky behavior. It also multiplies the risk of accidents: falls, drowning, road accidents. Acute intoxication can lead to a potentially serious alcohol-induced coma.

The effects roughly follow blood alcohol concentration. From 0.2 to 0.5 g/L, alcohol disinhibits, narrows the visual field, and lengthens reaction time, often without the person realizing it: they instead feel more confident. Between 0.5 and 1 g/L, movement coordination, balance, and speech deteriorate. Beyond that, vomiting, confusion, and sometimes “blackouts” appear: the brain stops recording memories, while the person keeps talking and acting. At higher levels, alcohol depresses the brain centers that control breathing and body temperature, which can lead to coma and, in extreme cases, death. These thresholds vary a lot from person to person depending on weight, sex, whether a meal was eaten, and drinking habits.

Behind the wheel, the risk of a fatal accident rises from low blood alcohol levels and increases rapidly with concentration. This is why the legal limit is set at 0.5 g/L in France, and 0.2 g/L for new drivers and commercial drivers.

Faced with someone unconscious after drinking, a few reflexes can save a life. Never leave the person alone or let them “sleep it off” on their back, since they risk choking if they vomit. Place them in the recovery position, cover them to prevent getting cold, and call emergency services, especially if their breathing is slow or irregular, if they don't respond, or if they may have taken other substances. In the US, call 911; in France, the equivalent is 15 or 112.

The next-day “hangover” is also a signal. Dehydration, the effect of acetaldehyde, inflammation, and poor-quality sleep all combine. Its effects on attention and reflexes often persist for several hours, even once blood alcohol has returned to zero.

In the United States, accidents, poisonings, and violence linked to alcohol account for a significant share of deaths, particularly among young adults. In France, by contrast, external causes (accidents and suicides) account for only about 13% of deaths attributable to alcohol. The large majority is due to the effects of regular, long-term consumption.

The cumulative effects of regular consumption

In the longer term, regular consumption beyond the recommended guidelines increases the risk of many diseases:

• Liver disease: from fatty liver to cirrhosis, via alcoholic hepatitis
• Certain cancers: mouth, throat, esophagus, liver, breast, colon
• Cardiovascular disease: a topic covered in detail in the next article on this blog
• Digestive and pancreatic disorders
• Effects on mental health: alcohol is sometimes used to ease anxiety or sleep problems in the short term, while worsening those same problems over time

The liver is the first organ affected, since it's the one that eliminates alcohol. Fat buildup in its cells, fatty liver, occurs in the vast majority of heavy drinkers. It causes no symptoms and remains reversible within a few weeks of stopping or sharply cutting back. If drinking continues, inflammation can set in, then fibrosis, that is scar tissue, which can progress to cirrhosis. This process generally takes many years. The Do I have fatty liver disease? test on the hub assesses fibrosis risk, whatever its cause.

Cancers are the leading cause of death attributable to alcohol in France. About 28,000 new cancer cases a year are estimated to be linked to it there, or nearly 8% of cancers. The mechanism mainly involves acetaldehyde, which damages cell DNA, and, for breast cancer, an increase in estrogen levels. The risk rises from low levels of consumption. For breast cancer, each additional daily drink increases it by about 7 to 10%. Combining alcohol with tobacco multiplies the risks for cancers of the mouth, throat, and esophagus.

The pancreas can develop acute pancreatitis, which is very painful, or chronic pancreatitis, eventually leading to poor digestion and sometimes diabetes. The nervous system can also suffer: pain and tingling in the legs (neuropathy), memory and balance problems, and, in the most severe forms linked to vitamin B1 deficiency, serious memory impairment.

Sleep and mood deserve special mention, because alcohol's effect here is deceptive. A drink in the evening helps you fall asleep, but it fragments the second half of the night and reduces REM sleep. You then wake up less rested, which feeds fatigue and irritability. Similarly, the relaxing effect on anxiety is followed by an anxiety rebound as the alcohol clears, which drives you to drink again. Regular consumption is also associated with an increased risk of depression. If this cycle sounds familiar, the Am I depressed? and Am I too sleepy? tests on the hub can help you take stock.

A substantial mortality toll, everywhere in the world

In France, alcohol is linked to about 41,000 deaths a year according to the latest estimate from Santé publique France, covering 2015. That represents nearly 7% of all deaths, placing alcohol among the very top causes of preventable death alongside tobacco. Among these deaths, about 16,000 are cancers, nearly 10,000 are cardiovascular diseases, 6,800 are digestive diseases, and 5,400 are accidents or suicides. Alcohol is involved in up to 15% of deaths among people aged 35-64. The study also shows that 90% of these deaths, excluding accidents, involve people drinking more than 5 drinks a day. The risk is therefore heavily concentrated among heavy drinkers, even though it exists from lower levels of consumption too.

In the United States, the CDC estimates about 178,000 annual deaths due to excessive alcohol use over 2020-2021. That is a 29% increase compared with 2016-2017, more pronounced among women (+35%) than men (+27%). These deaths shorten the lives of those affected by 24 years on average. A landmark study published in 2004 in JAMA (Mokdad et al.) already ranked alcohol as the third leading cause of preventable death in the country, behind tobacco and the combination of poor diet and physical inactivity.

Globally, the World Health Organization (WHO) estimates that alcohol caused 2.6 million deaths in 2019, or about 4.7% of all deaths worldwide. Of these, about 1.6 million are due to noncommunicable diseases, including cardiovascular disease and cancers, and more than 700,000 to injuries: road accidents, violence, suicides. Young adults are particularly affected: alcohol is involved in about 13% of deaths among people aged 20 to 39.

An impact that isn't limited to the person drinking

Beyond the direct health consequences for the person concerned, alcohol has wider repercussions: accidents involving third parties, violence, impact on the family circle. This blog isn't meant to go into these societal aspects in detail, but it's worth remembering that the question of alcohol consumption goes beyond the purely individual level.

Pregnancy is the most direct example. Alcohol crosses the placenta and reaches the fetus, whose developing brain is particularly sensitive to it. Prenatal exposure is the leading cause of non-genetic intellectual disability in France. Fetal alcohol spectrum disorders affect about 1% of births in Western countries, in their mildest forms. Since no amount is considered risk-free, the recommendation is simple: no alcohol during pregnancy, or when planning one.

Close family and friends are affected too. Growing up with a parent struggling with alcohol, or living with a partner who drinks too much, exposes someone to chronic stress, and sometimes to violence. Organizations like Al-Anon specifically support those close to someone with a drinking problem, and in France the Alcool Info Service helpline (0 980 980 930) responds to drinkers and to those around them alike. In the US, the SAMHSA National Helpline (1-800-662-4357) plays a similar role.

To estimate your own risk level, take the “Is my alcohol consumption risky?” test.