Relationship of systolic blood pressure with plasma homocysteine: importance of smoking status.
BACKGROUND
Elevated plasma homocysteine is a risk factor for cardiovascular disease. Elevations in plasma homocysteine occur in both smokers and hypertensives, but the combined effect of smoking and hypertension on homocysteine is unknown.


METHODS
Resting plasma homocysteine levels and blood pressure were determined in 56 normotensives (12 smokers) and 20 essential hypertensives (10 smokers).


RESULTS
Plasma homocysteine was significantly higher in all smokers versus all non-smokers (9.46 +/- 0.5 versus 7.9 +/- 0.5 micromol/l, P = 0.041) by two-way ANOVA, and was also significantly higher in all hypertensives versus all normotensives (9.8 +/- 0.6 versus 7.6 +/- 0.4 micromol/l, P = 0.004). There was no interaction between the effects of hypertension and smoking on plasma homocysteine. Hypertensive smokers had significantly higher plasma homocysteine than either normotensive non-smokers (10.65 +/- 0.84 versus 7.05 +/- 0.26 micromol/l), hypertensive non-smokers (7.88 +/- 0.64 micromol/l) or normotensive smokers (8.36 +/- 0.5 micromol/l). In subjects overall, homocysteine levels were correlated (r = 0.306, P = 0.015) with systolic blood pressure but not with diastolic (r = 0.186). This relationship was also significant in smokers, but not non-smokers. Furthermore, subjects in the highest quintile for plasma homocysteine had significantly higher systolic BP than those in the lowest quintile. This effect was not observed when smokers were removed from the analysis.


CONCLUSIONS
Smoking compounds the modest effect of hypertension on plasma homocysteine. The strong relationship between systolic blood pressure and homocysteine that exists only in smokers suggests that smoking-induced homocysteine elevations may raise systolic blood pressure. We speculate that smoking compounds the risk of cardiovascular disease in hypertensives, in part, by elevating homocysteine.
Kennedy
Brian P
BP
Department of Medicine, University of California, San Diego Medical Center, California 92103-8341, USA. bkennedy@ucsd.edu
Farag
Noha H
NH
Ziegler
Michael G
MG
Mills
Paul J
PJ
D001794:Blood Pressure; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000453:epidemiology*; D006973:Hypertension / Q000097:blood* / Q000453:epidemiology*; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*
D006710:Homocysteine