Poor working memory and reduced blood pressure levels in concurrent users of khat and tobacco

The purpose of this study was to examine the extent in which concurrent use of khat and tobacco was associated with decrements in working memory. We also tested whether cardiovascular activity during a cognitive task was related to performance outcomes, as research has shown linkages between maladaptive physiological adjustments and cognitive functions.

Seventy-four concurrent users of khat and tobacco, 49 khat-only users, and 52 nonusers (M age ± SD: 23.8±4.8) completed a laboratory session including 10 min of a mental arithmetic challenge task. Systolic blood pressure (SBP) and diastolic blood pressure and heart rate were collected throughout the task. Analyses of variance and correlational analyses were conducted.

We found that concurrent users evidenced the lowest number of correct responses on the math task among these 3 groups (ps < .05). Concurrent users also showed fewer number of attempts than khat-only users (ps < .01) and lower accuracy rate than nonusers (ps < .05). The performance of khat-only users and nonusers were comparable on these 3 measures (p > .76). Overall blood pressure levels were lower in concurrent users than in nonusers (p < .05). Correlational analysis found that lower SBP during the math task was associated with fewer number of correct responses and attempts and lower accuracy rate on the task (ps < .05). Multiple regression analysis controlling for gender found that concurrent use predicted math performance (ps < .05). Reported duration and frequency of khat and tobacco use and nicotine dependence predicted performance measures (ps < .05).

These findings suggest potential linkages between concurrent use of khat and tobacco and impaired working memory.