Academic journal article Alcohol Research

Focus on the Brain: HIV Infection and Alcoholism: Comorbidity Effects on Brain Structure and Function

Academic journal article Alcohol Research

Focus on the Brain: HIV Infection and Alcoholism: Comorbidity Effects on Brain Structure and Function

Article excerpt

Both HIV infection and alcohol abuse have negative effects on the brain, with some unique to each condition and others shared by both conditions. Investigators have used magnetic resonance imaging to study the size and integrity of various brain structures in participants with alcoholism, HIV infection, or both conditions and in healthy control subjects. In these studies, alcoholics exhibited enlarged, cerebrospinal fluid-filled spaces (i.e., ventricles) as well as tissue shrinkage in various brain regions (e.g., the corpus callosum and frontal cortex), whereas study participants with asymptomatic HIV infection showed few abnormalities. Those with both HIV infection and alcoholism also had these volume abnormalities, particularly if they had experienced an AIDS-defining event. Diffusion tensor imaging, which measures the integrity of white matter fibers, has identified abnormalities of constituents of these fibers in both diseases. Again, people with HIV infection plus alcoholism show the greatest abnormalities, particularly those with a history of an AIDS-defining event. Magnetic resonance spectroscopy, which assesses the levels of brain metabolites and selective neurotransmitters, has revealed different patterns of deficits in biochemical markers of brain integrity in individuals singly affected and a compounding of effects in individuals with both HIV infection and alcoholism. Finally, neuropsychological studies have revealed impairment in selective functions involving working memory, visuospatial abilities, and movement speed that are especially likely to occur in people with comorbid HIV infection and alcoholism. Thus, alcoholism is a major risk factor for development of neuropathology and its functional sequelae in HIV-infected people. KEY WORDS: Alcohol abuse; alcoholism; risk factors; human immunodeficiency virus; acquired immune deficiency syndrome; brain; brain function; brain structure; neuropathology; magnetic resonance imaging; diffusion tensor imaging

The incidence of alcohol abuse and dependence among individuals infected with human immunodeficiency virus (HIV) is high. Those with concurrent HIV infection and alcohol abuse are at risk of poorer clinical outcome for a variety of reasons that are described in detail elsewhere in this issue of Alcohol Research & Health. HIV infection and excessive alcohol use each have specific negative effects on central nervous system (CNS) structure, chemistry, and function, some of which are unique to each disease and some of which are shared. Thus, the brains of people with a history of excessive alcohol consumption are particularly vulnerable to further insult when newly exposed to the HIV virus. Continued excessive drinking can exacerbate the new liability from HIV infection, especially in those who develop an AIDS-defining event, such as severely low numbers of immune cells (i.e., CD4+ Tcell count under 200/mm3) targeted by HIV infection. The many factors affecting this dynamic interaction of effects of alcohol abuse and HIV infection on the brain are challenging to identify and disentangle but are likely to include the following: general health; cognitive status; age at HIV infection; length and severity of alcohol history before HIV infection; quantity, frequency and pattern of alcohol use after HIV infection; the lag between the HIV diagnosis and start of antiretroviral treatment; diligence in medication compliance; and whether other drugs of abuse are used.

One method for identifying how the effects of excessive alcohol use and HIV infection interact in the brain is to follow people with both active alcoholism and HIV infection and to compare changes in their cognition and brain status over time with changes in individuals with only one condition and control subjects with neither condition; this is known as a fourgroup comparison. Given the human condition, such studies (especially longitudinal ones entailing repeated examination of the same individuals over an extended time) are necessarily naturalistic and not ethically or practically amenable to formal experimental control over relevant variables, such as alcohol or illicit drug use, nutrition, medication, or risky behavior. …

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