"We know that chronic cigarette smoking and heavy drinking are common among people living with HIV," says lead author Timothy C. Durazzo, PhD, a research scientist in radiology at SFVAMC and an assistant professor of radiology at UCSF. "Chronic heavy drinking alone can injure the brain and lead to deficiencies in cognitive function, but it appears that cigarette smoking places an additional significant burden on the central nervous system of HIV-infected people who drink."
The study appears in the November 2007 issue of the journal Alcohol. The researchers compared neurocognitive test results and MRI brain scans from three groups: 17 HIV-infected heavy drinkers who were also chronic smokers, 27 HIV-infected heavy-drinking non-smokers, and 27 HIV-negative, light-drinking, non-smoking controls. None of the heavy drinkers were in treatment for alcohol use at the time of the study.
The study subjects were matched with the controls in age and other demographic factors. The two HIV-infected groups were matched as closely as possible in terms of medication, viral load, and other disease-specific measures. In neurocognitive testing, the HIV-infected heavy drinking smokers showed significantly poorer cognitive efficiency and auditory-verbal learning memory compared with the HIV-infected heavy drinking non-smokers. While both groups generally had poorer neurocognitive test results than the control group, the smoking
group demonstrated the greatest deficits.
In comparison with the controls, the smoking-plus-drinking group had significantly smaller brain volume -- indicating tissue atrophy -- in all areas except the occipital lobe, which governs vision. In contrast, the drinking non-smokers had smaller volume than the controls only in the frontal lobe, which plays a significant role in judgment and behavior.
Durazzo says that he and other researchers believe that cigarette smoke itself, rather than nicotine, is the likely culprit: "There are over 4,700 compounds in cigarette smoke, many of them quite toxic. This is not stuff you're going to want spread on your toast in the morning."
He observes that in addition to its neurocognitive effects, cigarette smoking is known to decrease immune system function as well as increase the likelihood of cancer. "When you already have a compromised immune system, as in HIV disease, the last thing you want to do is place an additional burden on it," he says.
"Our findings add to the growing body of research linking chronic smoking to brain injury and cognitive dysfunction," concludes co-principal investigator Dieter Meyerhoff, Dr.rer.nat., a senior researcher in radiology at SFVAMC and professor of radiology at UCSF. Durazzo and Meyerhoff have conducted several studies indicating that chronic cigarette smoking is associated with brain structural abnormalities and poor neurocognitive performance in heavy drinkers who do not have HIV.
Durazzo says that the result of the current study "is yet another reason that substance abuse treatment providers should strongly consider including strategies, treatments or referrals for smoking cessation for their patients who drink." However, he notes that while there is an increasing number of medications available to help people stop smoking, not enough is known about their effects on HIV-infected
"Every population faces unique challenges," he says. "We need more research in this area before we know if these medications have the same benefit for people living with HIV disease."