Effects of two benzodiazepines on the speed and accuracy of perceptual-motor performance in the elderly.

The daytime performance efficiency of 12 elderly subjects of average age 81.5 years (range 75-96 years) was examined in a cross-over study following lormetazepam 1 mg, nitrazepam 5 mg, and placebo capsules nightly for 7 nights. Performance was assessed on the Gibson spiral maze, and a reciprocal tapping task. In both tasks the speed and the accuracy of performance were independently measured. Performance testing sessions were conducted on the morning following the first, and the morning following the seventh dose of each of the three experimental treatments. Performance on the Gibson spiral maze showed no significant effect of either of the active drugs. On the reciprocal tapping task, speed was similarly unaffected by both drugs. However, while neither drug significantly affected overall accuracy after the first dose, nitrazepam but not lormetazepam significantly impaired overall accuracy after seven consecutive doses. This difference between nitrazepam and lormetazepam was significant. Further analyses showed nitrazepam consistently to be associated with impaired accuracy at both intermediate and high levels of task complexity. Lormetazepam, on the other hand, was associated with impairment only at the highest level of task complexity. The overall pattern of impairment associated with nitrazepam, but not with lormetazepam, was consistent with drug accumulation.