Stroke is the leading cause of death and disability among Chinese residents. Early screening of high-risk individuals in the community is crucial for primary prevention of stroke. However, the modifying effect of body mass index (BMI) on stroke risk associated with serum homocysteine (Hcy) remains controversial, and the lack of community-based data limits its application at the grassroots level.

To explore the association between Hcy and stroke-related risks in high-risk individuals in the community based on different BMI stratification.

A total of 1 154 contracted patients who visited the Fangzhuang Community Health Service Center in Fengtai District, Beijing, from April 2025 to February 2026, were consecutively enrolled as study subjects. The subjects were stratified by BMI into normal (18.5 kg/m²≤BMI<24.0 kg/m²), overweight (24.0 kg/m²≤BMI<28.0 kg/m²), and obesity (BMI≥28.0 kg/m²); by serum Hcy level into normal Hcy (<15 μmol/L) and hyper-Hcy (≥15 μmol/L); and by the number of risk factors into low-risk (0-2 items), moderate-risk (3-5 items), and high-risk (≥6 items) groups for stroke. The dual high-risk population was defined as subjects who simultaneously met the criteria of both the "hyper-Hcy group" and the "high-risk group". Univariate analysis, multivariate Logistic regression analysis, the Cochran-Armitage trend test, and subgroup and interaction effect analysis were employed to explore the association between Hcy and moderate-to-high stroke risk in the community population under different BMI stratification. Receiver operating characteristic (ROC) curves were used to evaluate the predictive value of Hcy and the combined indicator model for moderate-to-high stroke risk in the community population.

Among the included subjects, BMI stratification showed 504 (43.67%) in the normal group, 470 (40.73%) in the overweight group, and 180 (15.60%) in the obesity group. Regarding Hcy levels, 187 (16.20%) had hyper-Hcy and 967 (83.80%) had normal Hcy. For stroke risk stratification, there were 594 (51.47%) in the low-risk group, 525 (45.49%) in the moderate-risk group, and 35 (3.03%) in the high-risk group. In addition, 26 patients (2% of the total study population) were identified as the dual high-risk population, meeting the criteria of both the hyper-Hcy group and the high-risk group. After the moderate-risk group and the high-risk group were combined into the moderate-to-high risk group, univariate analysis showed statistically significant differences in gender, age, Hcy stratification, and BMI stratification between the moderate-to-high risk group and the low-risk group (P<0.001). Multivariate Logistic regression analysis showed that for every one-year increase in age, the risk of being in the moderate-to-high stroke risk group increased by 5% (OR=1.05, 95%CI=1.03-1.06, P<0.05); being female was a protective factor (OR=0.38, 95%CI=0.29-0.51, P<0.05); compared with individuals with normal BMI, the risk of being in the moderate-to-high stroke risk group increased by 64% in overweight individuals (OR=1.64, 95%CI=1.23-2.20, P<0.05) and by 8.58 times in obese individuals (OR=9.58, 95%CI=6.09-15.50, P<0.05); and compared with individuals with normal Hcy, the risk of being in the moderate-to-high stroke risk group increased by 9.50 times in hyper-Hcy individuals (OR=10.50, 95%CI=6.32-18.30, P<0.05). The Hosmer-Lemeshow test confirmed good model fit (χ²=6.182, P=0.624). The Cochran-Armitage trend test showed a significant dose-response relationship between Hcy levels and moderate-to-high stroke risk in the community population (P<0.001). No significant multiplicative or additive interaction was observed between Hcy and BMI (both P>0.05), and the risk effect was independent of BMI, gender, and age. ROC curve analysis showed that the optimal cutoff value of Hcy for predicting moderate-to-high stroke risk was 12.105 μmol/L, with an area under the ROC curve (AUC) of 0.707; the combined model incorporating Hcy, age, gender, and BMI achieved an AUC of 0.795 for predicting moderate-to-high stroke risk, indicating superior diagnostic performance.

Elevated serum Hcy, overweight, and obesity are all independent factors that increase the risk of being in the moderate-to-high stroke risk group in the community population. Moreover, under different BMI stratification, Hcy levels exhibit a significant dose-response relationship with moderate-to-high stroke risk in the community population, and the effect of Hcy on stroke risk is independent of BMI stratification.