Dramatic increases in the prevalence of chronic diseases, such as cardiovascular diseases and cancer, in developing countries represent a global challenge that could overwhelm health systems and economies in these countries. The escalation of chronic diseases is caused directly and indirectly by behavioral and environmental factors, including tobacco use [1,2]. In addition to current tobacco use, polysubstance use may occur, particularly in countries where cultural use of drugs is entrenched or where government is unstable [3].

Addressing tobacco use is critical to curbing the burden of disease globally, especially in low- and middle-income (LAMI) countries. Our current research in Yemen suggests that khat (Catha edulis) increases tobacco use and consequent harm. Khat trees grow at high altitudes in East African and Middle Eastern countries, and we propose that the possible interactions of khat and tobacco and the stimulant-like agents (cathinone and nicotine) may have additive biological and behavioral effects.

Coronary heart disease, stroke and cancer have increased greatly in Yemen over the last decade [4]. Epidemiological surveys report tobacco use prevalence at 60–77% among adult men and 25–29% (but escalating) among adult females [5]. Tobacco smoking by women and adolescents is common via waterpipes (hookah); such use by women is due partly to disapproval of public cigarette smoking. Waterpipes may slightly reduce nicotine per puff, but smokers titrate upwards, obtaining doses comparable to cigarettes, thus conferring similar risk [6].

Historically used for medicinal purposes, khat's stimulant effects are valued in social contexts. Chewing fresh leaves during 2–5-hour afternoon sessions is common, with effects including increased alertness, concentration, confidence, friendliness, contentment and flow of ideas. Cathinone is an amphetamine-like sympathomimetic amine causing heart rate and blood pressure increases [7,8]. Clinical observations suggest increased risk for acute myocardial infarction and stroke in khat users [9–11].

During khat-chewing sessions, large quantities of tobacco may be smoked. A study of Yemeni medical students reported that 42% of khat chewers were heavy smokers (>20 cigarettes/day) [5]. Other regional data note tobacco use reaching 62% among khat users [12,13]. No research has systematically evaluated acute or chronic effects of the cathinone–nicotine combination. A US National Institutes of Health (NIH) collaborative with scientists from the United Staes, European Union, Africa and the Middle East has established the ongoing Khat Research Program (KRP).

Unpublished data and anecdotal evidence suggests high khat–tobacco use prevalence in Yemen. Observation suggests the possibility that khat use increases tobacco use risk, pointing to a needed evaluation of khat–tobacco interactions, behavioral and biological mechanisms and determining whether concurrent use exacerbates problems in cessation. Khat use reduction strategies have not been explored, but identification of antecedents and consequences of concurrent khat–tobacco use will guide eventual prevention and treatment development drawing upon, and informing, the broader polysubstance use field.


  1. Top of page
  2. Funding
  3. Acknowledgements
  4. References

Dr al'Absi was supported in part by the following grants for this work: a FIRCA grant from the National Institutes of Health/Fogarty International Center (R03TW007219), an R21 National Institute for Drug Abuse grant (DA024626), and a grant from the Office of International Programs at the University of Minnesota.


  1. Top of page
  2. Funding
  3. Acknowledgements
  4. References

We thank KRP team members in Yemen, including Drs Mohamed Al Soofi, Anisa Dokam, Najat Saem Khalil, Molham Al Habori and Abed Naji Kasim


  1. Top of page
  2. Funding
  3. Acknowledgements
  4. References
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    World Health Organization (WHO) Expert Committee on Drug Dependence. WHO Technical Report Series, No. 915—Thirty-Third Report 2009. Geneva: WHO; 2009.
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    United Nations Office on Drugs and Crime (UNODC). World Drug Report 2010: drug use is shifting towards new drugs and new markets. Vienna: UNODC; 2010.
  • 4
    World Health Organization (WHO). Chronic Diseases Are the Major Cause of Death and Disability Worldwide. Geneva: WHO; 2011.
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    Bawazeer A. A., Hattab A. S., Morales E. First cigarette smoking experience among secondary-school students in Aden, Republic of Yemen. East Mediterr Health J 1999; 5: 4409.
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