Dose–response relationship between khat chewing frequency and sleep duration, perceived effects, and academic performance among medical students in Yemen

Although khat chewing is common among university students in Yemen, evidence on dose–response relationships between khat chewing frequency and sleep duration, perceived effects, and academic performance remains limited. This study examined these associations among medical students at Thamar University, Yemen. A cross-sectional study was conducted among undergraduate medical students. Data were collected using a structured questionnaire. Khat chewing frequency was categorized as non-use, 1–2 days/week, 3–4 days/week, and 5–7 days/week. Multivariable logistic and linear regression analyses were performed to assess associations, and ordinal trend analyses were used to evaluate dose–response relationships. Adjusted odds ratios (AOR) and regression coefficients (β) with 95% confidence intervals (CI) were reported. Statistical significance was set at p < 0.05. Increasing khat chewing frequency was independently associated with higher odds of short sleep duration (< 6 h). Compared with non-chewers, the adjusted odds of short sleep increased progressively, reaching an AOR of 7.83 (95% CI: 3.70–16.57; P < 0.001) among daily chewers.A significant linear dose–response relationship was also observed (AOR = 1.97, 95% CI: 1.54–2.52; P < 0.001). Perceived-effects scores increased progressively with khat-chewing frequency, with adjusted mean differences of 3.36, 3.73, and 4.94 for 1–2, 3–4, and 5–7 days/week, respectively (all P ≤ 0.001), with a significant linear trend (adjusted β = 1.61, 95% CI: 1.29–1.92; P < 0.001). In contrast, academic performance showed no significant association or linear dose–response relationship with khat chewing (adjusted β = 0.22, 95% CI: −0.46–0.89; P = 0.532). Khat chewing frequency showed clear dose–response associations with short sleep duration and perceived effects among medical students. However, these associations did not translate into measurable differences in academic performance. These findings suggest that the effects of frequent khat use are more evident in sleep and perceived behavioural outcomes than in academic achievement. These findings are consistent with known stimulant-related effects and may extend to similar student populations in comparable settings.