Risk factors of stroke at high and low altitude areas in Saudi Arabia

The epidemiology of stroke at different geographical locations in the Kingdom of Saudi Arabia has not been adequately investigated.

In this study, clinical types and risk factors of stroke were compared among patients at low-altitude (Riyadh, 620 m) and high-altitude (Al Baha > 2000 m) areas using a case-control study design. One-hundred ninety recently diagnosed cases (109 from Riyadh and 81 from Al Baha) were verified and subjects were interviewed. An equal number of age- and sex-matched controls from the corresponding areas were also interviewed using a specific standard questionnaire.

The frequency of thrombotic stroke at high altitude was 93.4% as compared to 79.3% at low altitude (P < 0.05). The odds ratios (OR) for the different risk factors at high and low altitudes, respectively, were: hypertension 4.4 and 2.1; diabetes mellitus: 2.7 and 1.9; ischemic heart disease (IHD): 2.4 and 1.9; atrial fibrillation: 3.9 and 3.3, and smoking: 2.3 and 2.5. The mean hematocrit values were 45.3% at high altitude and 41.0% for low altitude patients (P < 0.001) and its association with stroke at high altitude remained significant even after adjusting for age, gender and occupation.

The study's finding of an increased frequency of thrombotic stroke at high altitude was explained by increased hematocrit which might have caused this in conjunction with other factors such as hypertension and IHD. Larger studies are recommended for better clarification of interaction between high altitude and other established risk factors not included in this study, such as sickle cell anemia and congenital heart diseases in young patients.