Khat as a risk factor for hypertension: A systematic review.
BACKGROUND
Studies suggest possible newer risk factors for hypertension including Khat chewing, a plant which grows wild in countries bordering the Red Sea and along the east coast of Africa and the Arabian Peninsula.


OBJECTIVE
The objective was to synthesise the best available evidence on the epidemiological association between Khat chewing as exposure (potential risk factor) and hypertension.


METHODS
Subjects aged 16 years old or older regardless of gender and ethnicity, country of residence, Khat dose, frequency, duration of chewing or other characteristics of Khat exposure and co-presence of other known risk factors for hypertension.The focus of interest of this review was the epidemiological association between Khat chewing as exposure (potential risk factor) and hypertension as an outcome.Observational analytical studies (cohort studies, case-control studies and cross-sectional studies) were considered for inclusion.


METHODS
Three staged search strategy was used to identify all relevant published and grey literature in English language from 1988 to 2011. Databases searched were PubMed, CINAHL, PopLine, LILACS, MedNar and Embase.


METHODS
All papers selected for inclusion in the review were subjected to a rigorous, independent appraisal by the two reviewers prior to inclusion in the review using standardised critical appraisal instruments from the Joanna Briggs Institute.


METHODS
Due to poor internet service in our setting we were unable to use the Joanna Briggs Institute -software for data extraction and synthesis as approved in the protocol. Quantitative papers were pooled in statistical meta-analysis using the Review Manager Software. Odds ratios and their 95% confidence intervals were calculated for analysis.


RESULTS
Two studies from Ethiopia and one from Saudi Arabia were identified. In the study done by Getahun et al. 44 of the chewers (n=324) and 34 of the non chewers (n=319) were found to have hypertension. Analysis of this study showed no statistically significant association between Khat chewing and hypertension (OR=1.29, 95% CI =0.80-2.08). In the second study done by Mossie, 29 of the chewers (n=277) and 73 of the non chewers (n=621) were found to have hypertension and there was no statistically significant association between Khat chewing and hypertension (OR=0.88, 95% CI =0.56-1.38). Seventy seven of the chewers (n=568) and 160 of the non chewers (n=1207) were found to have hypertension) in the third study done by Ibrahim, similarly there was no statistically significant association between Khat chewing and prevalence of hypertension (OR=1.03, 95% CI =0.77-1.37 in this study.On meta analysis, a total of 3321 subjects were involved. Of the Khat chewers (1174), 150 were found to have hypertension. On contrary, 267 of non chewers (2147) were found to have hypertension. Finding of the analysis showed no statistically significant association between Khat chewing and hypertension (Odds ratio=1.04, 95% Confidence Interval= 0.84, 1.29). The studies were homogenous, Heterogeneity test: Chi = 1.35, df = 2, (P = 0.51). The test for overall effect also showed no statistical significance at conventional levels (P>0.05).


CONCLUSIONS
We did not find sufficient evidence to conclude that Khat as epidemiologic risk factor for hypertension.The present systematic review did not identify a statistically significant association of Khat chewing as epidemiologic risk factor for hypertension.


CONCLUSIONS
This review identifies the need for further studies on Khat as an epidemiologic risk factor for hypertension considering further aspects of chewing, like dose-response, duration of chewing and co-existence of other co-morbid factors of hypertension.
1. Lecturer of Physiology, Department of Biomedical Sciences Jimma University, P.O.Box 378, Jimma, Ethiopia 2. Lecturer of Reproductive Health, Department of Population and Family Health Jimma University, P.O. Box 378, Jimma, Ethiopia E-mail: misra_ab@yahoo.com 3. Lecturer, Department of Epidemiology, College of Public Health and Medical Sciences, Jimma University, Email: tariku.dejene@ju.edu.et 4.Associate Professor, Department of Health Services Management, College of Public Health and Medical Sciences, Jimma University, Email: mirkuzie@yahoo.com 5. Professor, Dept. of Health Education and Behavioral Sciences, Director, The Ethiopian Malaria Alert Centre: a collaborating centre of the Joanna Briggs Institute Ethiopia - Joanna Briggs Center for Evidence Synthesis, College of Public Health and Medical Sciences, Jimma University, P. O. Box - 378, Jimma, Ethiopia, Email: morankarsn@yahoo.com sudhakar.morankar@gmail.com.
Kalkidan
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Hassen
Misra
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Abdulahi
Tariku
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Sudhakar