Poor sense of smell among alcoholics associated with prefrontal cognitive dysfunction

Prior research has shown that chronic alcoholism is associated with numerous olfactory deficits in odor judgment, odor identification, odor sensitivity, and the ability to qualitatively discriminate between odors.

New findings indicate that olfactory deficits among alcoholics are associated with prefrontal cognitive dysfunction, specifically, impairment in the functional integrity of the prefrontal lobe.

Results are published in the August issue of Alcoholism: Clinical & Experimental Research.

"Both frontal and medial temporal lobe brain regions play a major role in olfactory functioning, particularly in the abilities of odor quality discrimination and identification," said Claudia I. Rupp, clinical neuropsychologist and assistant professor in the department of psychiatry at Innsbruck Medical University, and corresponding author for the study.

"Given that alcohol can cause brain damage and dysfunction in frontal and medial temporal brain regions, and that neuropsychological tasks such as executive function and memory may represent sensitive measures of the integrity of these brain areas, we were interested in whether olfactory deficits in alcohol dependence are related to executive dysfunctions or memory impairments," she said.

Rupp and her colleagues examined 32 alcoholics (18 males, 14 females) and 30 healthy "controls" (16 males, 14 females) that were matched on age, gender and smoking status. All participants were assessed in three areas: olfactory function (detection threshold, quality discrimination, identification), executive function (using the Wisconsin Card Sorting Test), and memory (using the German version of the California Verbal Learning Test).

"We found that the alcoholics, when compared to the controls, were impaired in all three domains investigated: olfactory functions, executive function, and memory," said Rupp. "We also found that impairments in all three domains appear resistant to early recovery after alcohol drinking stopped. Furthermore, olfactory discrimination deficits appear to be associated with executive function impairment. Collectively speaking, our results suggest that olfactory discrimination deficits and executive function impairment may share a common neural substrate - that is, a pathological process may be mediating both deficits - most likely dysfunctional mechanisms involving the frontal lobe."

Rupp said that her findings help support the hypothesis that frontal lobes are particularly vulnerable to alcoholism-related damage, and that dysfunction in this region may play a significant role in alcoholism and other drug addictions. "Our findings add to the mounting evidence for frontal lobe dysfunction in alcoholism, which may be involved in the development of addiction, may mediate recovery in persons with alcohol-use disorders, and may play a key role in understanding the neurobiology of alcoholism," she said.

Rupp added that her study's findings raise some serious clinical concerns. "Olfactory dysfunction can seriously impair people in their day-to-day activities and occupation, increase their risk of injury or even death, and reduce their overall quality of life," she said. "These deficits may not only reduce patients' enjoyment of foods, but may also place them at risk for long term nutritional or health sequelae. Individuals may alter food choices and intake, resulting in weight loss, challenged immunity and impaired nutritional status  all of which are commonly observed in patients with chronic alcoholism. Nutritional deficiencies, moreover, also have notorious deleterious effects on brain structure and cognitive functioning. Future research needs to investigate the functional impact of olfactory dysfunction in alcohol dependence."

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