Volume 11 — May 22, 2014
ORIGINAL RESEARCH
Habitual Khat and Concurrent Khat and Tobacco Use Are Associated With Subjective Sleep Quality
The scatter plot shows a positive correlation between Pittsburgh Sleep Quality Index global score and negative mood. Participants who reported having greater sleep problems were more likely to have enhanced negative mood (r squared = .12, P < .001).
Figure 1. Association between sleep disturbances as measured by the Pittsburgh Sleep Quality Index (20) and negative mood as measured by a subjective mood questionnaire (25).
| Characteristic | Nonusers | Khat-Only Users | Concurrent Users of Khat and Tobacco |
|---|---|---|---|
| Global PSQI score, mean (standard error of the mean) | 3.38 (0.33) | 5.99 (0.29) | 6.45 (0.27) |
| Poor sleepers, % | 25.0 | 54.6 | 57.0 |
P < .001 for difference between nonusers and khat-only users. P < .001 for difference between nonusers and concurrent users of khat and tobacco. P < .63 for difference between khat-only users and concurrent users of khat and tobacco.
Figure 2. Differences in subjective sleep quality as a function of khat and tobacco use status. Sleep quality measured using the Pittsburgh Sleep Quality Index (PSQI) (20). In Figure 2a, values are the mean, and the I-beam lines in each bar indicate standard error of the mean. In Figure 2b, entries show percentages of participants classified as poor sleepers as determined by global PSQI scores greater than 5
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