National Institute on Alcohol Abuse and Alcoholism No. 15 PH 311 January 1992
Alcohol and AIDS
There are two reasons to investigate connections between alcohol, HIV infection, and AIDS: alcohol may adversely affect the immune system, and alcohol may influence high-risk sexual behavior.
Human immunodeficiency virus (HIV) is the agent that causes acquired immunodeficiency syndrome (AIDS). HIV is transmitted through sexual contact with an infected individual, through exchange of infected blood or blood products, or to the newborn from an infected mother. HIV-infected persons may harbor the virus for many years with no clinical signs of disease. Eventually, HIV destroys the body's immune system, mainly by impairing a class of white blood cells whose regulatory activities are essential for immune protection. As a result, people who have AIDS are prone to lung infections, brain abscesses, and a variety of other infections caused by microorganisms that usually do not produce disease in healthy people. Those who have AIDS also are prone to cancers such as Kaposi's sarcoma, a skin cancer rarely seen in non-HIV-infected populations. The diagnosis of AIDS depends in part on the presence of one or a number of these infections and cancers (1).1
One million people in the United States are estimated to be infected with HIV (2). At least 40,000 new HIV infections are thought to occur among adults and adolescents, and an estimated 1,500 to 2,000 new HIV infections are thought to occur among newborns each year. Currently, 8 to 10 million people worldwide are estimated to be infected with HIV (3). Of these, 50 percent are expected to develop AIDS within 10 years, and 90 percent may develop AIDS within 20 years of initial infection (4). The prognosis for persons with AIDS is grim: AIDS-associated mortality may approach 85 percent within 5 years of diagnosis (5).
Alcohol and the Immune System
Alcohol can impair normal immune responses that protect the body from disease (6,7,8). Chronic alcohol consumption has been shown to reduce the number of infection-fighting white blood cells in laboratory animals (9,10,11) and in humans (12,13). Chronic alcohol ingestion or alcohol dependence can depress antibody production and other immune responses in animals (10,9) and in humans (14,15). Alcohol can suppress activities of certain immune system cells, called macrophages, that help keep the lungs free from infection (16,17). In addition, alcoholics appear to be more susceptible to bacterial infections and cancer than are nonalcoholics (18,19). Studies in animals and in humans indicate that consuming alcohol during pregnancy can decrease immune resistance in the offspring (20,21,22).
Alcohol's generally immunosuppressive effects could mean that 1) drinking may increase vulnerability to HIV infection among people exposed to the virus, and that 2) among people who are already HIV infected, alcohol-induced immunosuppression might add to HIV-induced immunosuppression, and speed the onset or exacerbate the pathology of AIDS-related illness. These are complex ideas and areas of intense investigation, but so far only a few studies have been published. Researchers have learned that alcohol can impair white blood cell responses to HIV (23). A provocative study that warrants replication found that a single drinking episode depressed certain immune responses of white blood cells taken from healthy volunteers (24). In addition, white blood cells isolated after this drinking episode were more susceptible to HIV infection than were cells isolated from subjects who did not drink, hinting that even occasional alcohol consumption may increase the likelihood of infection upon exposure to HIV. Whether alcohol use influences the progression of AIDS in persons already infected with HIV has bee n explored in a recent study of homosexual men (25). While these researchers found that neither alcohol nor other drugs seem to influence the progression of HIV infection or the development of AIDS, their results await confirmation. Clearly, more research is needed to understand alcohol's role in HIV infection and the course of ensuing disease.
Alcohol and Sexual Behavior
Sexual practices considered to be high risk for acquiring HIV from an infected individual include vaginal or anal intercourse without a condom; other sexual practices that facilitate exchange of blood, semen, or other body secretions; and unprotected sexual activities with multiple partners. The frequency with which sexual partners engage in such practices also influences the risk for exposure to HIV.
Alcohol's relationship to high-risk sexual behavior may be explained in two ways. First, alcohol use may be a marker for a risk-taking temperament: those who drink alcohol may also engage in a variety of high-risk activities, including unsafe sexual practices, as a part of a "problem behavior syndrome" (26,27). Second, alcohol may influence high-risk behaviors at specific sexual encounters by affecting judgment and disinhibiting socially learned restraints (28,29). These are not mutually exclusive interpretations.
In addition, these two explanations have different implications for the prevention of high-risk sexual behavior. Among people who have a risk-taking temperament, reducing alcohol consumption may not reduce high-risk sexual behavior. However, among those who are more likely to take sexual risks when they are drinking than when they are not, reducing alcohol consumption should also reduce high-risk sexual behavior.
There are two approaches to studying alcohol's relationship to sexual behavior that may result in HIV infection (30). One approach examines whether alcohol use in general is correlated with sexual risk-taking behavior in general. In this approach, an observed association between drinking and high-risk sexual activity could imply that these two behaviors are part of a larger risk-taking tendency, or that alcohol itself influences sexual risk-taking, or both. Another approach examines the consequences of alcohol use during specific sexual encounters. An observed connection between alcohol use and sexual risk-taking during specific encounters suggests a direct influence of alcohol on such behavior.
A number of studies have identified associations between drinking and high-risk sexual activity. These studies also have found that an absence of or a reduction in alcohol use is associated with a decrease in high-risk sexual behavior. A study of heterosexual drinking habits and sexual behavior found that women and men who frequently combined alcohol use with sexual encounters were generally less likely to use condoms during intercourse (31). Similarly, a study of homosexual men found alcohol or other drug use combined with sexual activity to be strongly associated with high-risk sexual behavior: even those who drank only occasionally at the time of sexual encounters were twice as likely to be categorized as "high risk," based on the frequency of involvement in a range of sexual practices within nonmonogamous relationships, than were those who did not drink (32). Further, those men who did not drink during sexual encounters were three times more likely to be classified in a "no risk" category than were men who combined drinking with sexual activity. Recently, a reduction in alcohol use among homosexual men has been associated with a reduction in high-risk sexual behavior (33).
Other studies that examine the consequences of alcohol use at specific sexual encounters also have demonstrated a connection between alcohol use and high-risk sexual behavior. Scottish adolescents who drank at the time of first intercourse were less likely to have used a condom than those who did not drink (34). A survey of adolescents in M assachusetts revealed that teens were less likely to use condoms if sexual activity followed drinking or other drug use (35). Similarly, adult homosexual men and heterosexual women (but not heterosexual men) reported that they were less likely to use a condom during those sexual encounters in which they felt intoxicated (36). These reports of simultaneous alcohol use and high-risk sexual behavior suggest that alcohol can directly influence sexual risk-taking. However, these combined behaviors may still reflect a risk-taking tendency in some individuals.
Further research is needed to define conditions under which alcohol use is linked to high-risk sexual activity. Information generated from such studies will be vital for developing and improving programs to prevent HIV transmission.
Alcohol and AIDS--A Commentary by
NIAAA Director Enoch Gordis, M.D.
Science has made remarkable progress in our understanding of HIV and AIDS. Yet we know very little about the role of alcohol in the transmission and acquisition of HIV or in the progression of HIV infection to AIDS. Such knowledge would enhance efforts to prevent HIV exposure and decrease the number of new AIDS cases.
We know that alcohol affects the immune system. This suggests that alcohol could affect the course of HIV infection and AIDS, which is a disease of the immune system. For example, alcohol might affect the body's ability to defend against HIV infection upon exposure to the virus; alcohol might alter the course of infection to the development of AIDS; or alcohol might affect the severity or duration of the special infections, known as opportunistic infections, that characterize AIDS. So far, the research findings in this area are hard to reconcile. On one hand, laboratory evidence shows clearly that alcohol impairs the ability of white blood cells to defend against the human immunodeficiency virus. On the other hand, studies involving human populations have found that neither alcohol nor other drugs modify the course of HIV infection or AIDS. Given the complexity of the human immune system, the contradictions presented by these findings, while puzzling, are not unexpected. One key to solving this puzzle will be more attention, in long-term studies of human populations, to objective evidence of drinking and to laboratory evidence of immune function status.
We know also that alcohol is associated with high-risk sexual activity that potentially can result in exposure to HIV. Some people may be more likely to engage in certain sexual behaviors when drinking as a result of alcohol's disinhibiting effects. (In others, alcohol use and unsafe sexual practices seem to be a part of a "risk-taking temperament," in which unsafe sexual practices may occur whether or not alcohol is consumed.)
Prevention efforts that address the link between alcohol consumption and unsafe sex are being evaluated for their effectiveness in reducing high-risk sexual activity. In addition, researchers are investigating various settings, such as bars and alcohol treatment programs, and certain groups, such as teenagers, where intervention strategies could be employed to decrease alcohol-related high-risk sexual activity. It is hoped that these findings will help target HIV-related prevention strategies in a way that will help to reduce the incidence of new cases of HIV infection, and ultimately reduce the number of persons with AIDS.
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Updated: October 2000