Component cognitive and motor processes of the digit symbol test: differential deficits in alcoholism, HIV infection, and their comorbidity.

BACKGROUND

Alcoholism (ALC) is highly prevalent in patients with human immunodeficiency virus (HIV) infection (HIV), and those with comorbidity (ALC+HIV) may suffer compounded deficits in cognitive and motor functions affected by both conditions. Given that each disease can adversely affect motor, visuospatial, and executive functions, we used an expanded version of the Digit Symbol (DS) test to assess the separate and combined effects of ALC and HIV infection on these cognitive and motor components.

METHODS

Participants were 44 ALC, 43 HIV, 55 ALC+HIV, and 49 normal controls (NC). We modified DS test administration to assess sustained attention (grid completion speed), associative learning (number of boxes completed in 15-second epochs), and incidental learning (total number-symbol pairs correctly recalled) and also used ancillary tests of fine motor, visuospatial, and executive functions to assess their relationship with the different components of DS performance. All scores were corrected for age and education based on NC performance.

RESULTS

Neither single diagnosis group-ALC nor HIV-was impaired on DS score or grid completion speed compared with the NC group, but the dual-diagnosis ALC+HIV group was impaired. Greater lifetime alcohol consumption was associated with longer grid completion time in both ALC and ALC+HIV. The HIV group demonstrated associative learning on DS but ALC+HIV and ALC did not. All groups performed similarly on incidental learning. Multiple regression analyses demonstrated that executive functions, assessed by Color Trails 2, predicted traditional DS performance in all groups. Fine Finger Movement additionally predicted traditional DS performance and grid completion speed in HIV. Visuospatial function, assessed by ability to copy the Rey-Osterrieth complex figure, did not contribute independently to DS performance in either alcohol group.

CONCLUSIONS

Alcoholism combined with HIV infection resulted in deficits in visuospatial psychomotor function, as assessed by the DS test, although deficits were not observed in either disease condition alone. Neither alcohol group showed associative learning, and both had compromised sustained attention. Combined cognitive and motor adverse effects of alcoholism and HIV infection were manifest in psychomotor speed, sustained attention, and associative learning of visuospatial material and are testimony to the dangers of alcohol abuse even in relatively healthy patients with HIV infection.