Background: Hyperhomocysteinaemia and other risk factors associated with blood pressure have been reported in large community-based studies in different populations. However, it is not fully established whether hypertension is associated with high plasma total homocysteine levels (tHcy) or components of the homocysteine re-methylation pathway including vitamin B(12), plasma 5-methyltetrahydrofolate (5-MTHF) or red blood cell (RBC) 5-MTHF.
Aim: In this study we tested the hypothesis that RBC 5-MTHF could be a marker for long-term folate status in the blood and low RBC 5-MTHF may be associated with hypertension.
Methods: This was a cross-sectional study in a community-based setting and 492 males and 431 females were investigated. Systolic and diastolic blood pressures were determined and fasting blood samples were taken for determination of plasma tHcy, creatinine, uric acid, lipids, plasma 5-MTHF, RBC 5-MTHF and vitamin B(12).
Results: In males, the risk of hypertension was significantly (95% CI 1.9, 8.7; p = 0.003) increased by 1.8-fold in the first quartile compared with the highest quartile of RBC 5-MTHF when adjusted for body mass index (BMI), age, dyslipidaemia, uric acid, creatinine, smoking, plasma tHcy and vitamin B(12). The risk of hypertension was also significantly increased (95% CI 1.1, 9.2; p = 0.03) by 1.1-fold in the highest quartile compared with the lowest quartile of plasma tHcy when adjusted for BMI, age, dyslipidaemia, uric acid, creatinine, smoking, plasma and RBC 5-MTHF and vitamin B(12). There were no associations of hypertension with plasma tHcy, and other components of the Hcy re-methylation pathway were observed in females.
Conclusions: The association between hypertension and low RBC 5-MTHF was stronger than any other components of the homocysteine re-methylation pathway. Results from this study suggest that folate measurements in RBC seem to be the most reliable marker indicating 5-MTHF deficiency and disturbances in the Hcy re-methylation pathway in association with hypertension.