Objectives: Co-existence of hypertension and high homocysteine (HHcy) is associated with a higher risk of stroke. It is not known whether combination of hypertension and HHcy impacts on stroke-related neurological severity. Our aim was to determine whether there is an interaction of hypertension and HHcy on neurological severity in first-ever ischemic stroke patients. Methods: We analyzed neurological severity among 189 consecutive first-ever ischemic stroke patients with or without hypertension or HHcy. Results: By multiple logistic regression analysis, hypertension [odds ratio (OR): 8.086, 95% confidence interval (CI): 3.596 to 18.181, P < 0.001] and total homocysteine (tHcy) (OR: 1.403, 95% CI: 1.247 to 1.579, P < 0.001) were independently associated with moderate/severe neurological severity. In receiver-operating characteristic analysis, tHcy was a significant predictor of moderate/severe neurological severity (area under the curve 0.794; P < 0.001). A multiplicative interaction of hypertension and HHcy on more severe neurological severity was revealed by binary logistic regression (OR: 13.154, 95% CI: 5.293 to 32.691, P < 0.001). Multinomial logistic regression analysis further identified a more than multiplicative interaction of hypertension and HHcy on neurological severity compared with patients without each condition (OR: 50.600, 95% CI: 14.775 to 173.285, P < 0.001). Interaction effect measured on an additive scale showed that 76.4% patients was attributed to interaction of hypertension and HHcy in all patients with moderate/severe neurological severity. Conclusion: Significant interaction of hypertension and HHcy on neurological severity was found on not only multiplicative but also additive scale in first-ever Chinese ischemic stroke patients.
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