Plasma Vitamin B12 Level as a Potential Cofactor in Studies of Human Immunodeficiency Virus Type 1--Related Cognitive Changes

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Abstract
• Studies of cognitive function in subjects with human immunodeficiency virus type 1 (HIV-1) infection who remain relatively asymptomatic (ie, Centers for Disease Control stages II and III) have provided widely variable estimates of cognitive impairment. In view of the finding that approximately 25% of asymptomatic HIV-1—infected subjects demonstrate either marginal or overt vitamin B12 deficiency, we have investigated plasma vitamin B12 status as a potential cofactor in studies of HIV-1—related cognitive impairment. When cognition was assessed in asymptomatic (Centers for Disease Control stages II and III) HIV-1—infected participants taking into consideration vitamin B12 status, those subjects with low plasma vitamin B12 levels (12 status on specific measures of information processing speed and visuospatial problem-solving skills. These findings suggest that concurrent vitamin B12 deficiency may be a cofactor in subtle cognitive changes observed in the asymptomatic stages of HIV-1 infection. These differences in prevalence of low plasma vitamin B12 levels may help to explain differences among studies in the proportion of HIV-1—infected subjects showing cognitive impairment.