Role of Blood Pressure on Stroke-Related Mortality: A 45-Year Follow-Up Study in China
Introduction Hypertension is a significant public health concern in China, with a high prevalence and low rates of awareness, treatment, and control. It is a well-established risk factor for cardiovascular diseases, particularly stroke-related mortality. Despite the known association between high blood pressure (BP) and stroke, the long-term relationship between BP changes and stroke-related mortality, as well as the underlying mechanisms, remain poorly understood. This study aimed to explore the long-term causal associations between BP and stroke-related mortality and to investigate potential mediating and moderating factors influencing these associations.
Methods This study is a 45-year follow-up cohort study initiated in 1976, involving 1,696 participants from the Xi’an Machinery Factory in China. The participants were followed until 2020, with data collected at regular intervals. Blood pressure was measured twice at 10-minute intervals using a mercury-stand sphygmomanometer, and the average value was recorded. Hypertension was defined as systolic blood pressure (SBP) ≥140 mmHg or diastolic blood pressure (DBP) ≥90 mmHg. The study categorized BP into four groups based on SBP/DBP levels: <130/<80 mmHg, 130–139/80–89 mmHg, 140–159/90–99 mmHg, and ≥160/≥100 mmHg. Changes in BP from 1976 to 1994 were also analyzed.
The primary outcome was stroke-related mortality, determined using ICD-10 and ICD-11 codes. The study adjusted for various covariates, including age, sex, body mass index (BMI), marital status, education, occupation, smoking, drinking, diabetes, and total cholesterol (TC). Statistical analyses included Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for stroke-related mortality. Mediation and moderated mediation analyses were performed to explore the potential pathways through which BP influences stroke-related mortality.
Results Baseline Characteristics The study included 1,696 participants with an average age of 44.38 years, of which 66.3% were men. At baseline, 36.4% of participants had hypertension, with higher BP levels associated with older age, higher TC, and higher BMI. Over the 45-year follow-up period, 201 stroke-related deaths occurred, resulting in a mortality rate of 11.9% and an incidence density of 0.26 per 100 person-years. The incidence density of stroke-related mortality was significantly higher in participants with hypertension and in men compared to women.
Associations Between BP and Stroke-Related Mortality The Cox proportional hazard model revealed that participants with SBP ≥160 mmHg or DBP ≥100 mmHg at baseline had a 217.5% increased risk of stroke-related death (HR = 3.175, 95% CI: 2.297–4.388). This association was more pronounced in male participants. Similarly, participants who maintained hypertension from 1976 to 1994 had a 110.4% increased risk of stroke-related death (HR = 2.104, 95% CI: 1.632–2.713), with higher HRs observed in men.
Changes in BP and Stroke-Related Mortality Changes in BP categories from 1976 to 1994 were significantly associated with stroke-related mortality. Participants who transitioned from normal BP to hypertension or maintained hypertension had higher risks of stroke-related death compared to those who maintained normal BP. The adjusted HR for the hypertension → hypertension group was 2.104 (95% CI: 1.632–2.713), with higher HRs in male participants.
Mediation and Moderated Mediation Analysis BMI in 1994 was found to mediate the association between SBP in 1976 and stroke-related deaths in 2020, accounting for 10.1% of the total effect. The moderated mediation analysis further revealed that the direct effect of SBP on stroke-related death was moderated by gender, with the mediating effect being more significant in male participants. The mediating effect accounted for 5.81% of the total effect when considering the moderating role of gender.
Sensitivity Analysis The sensitivity analysis, using E values, indicated that the observed associations were robust, with most E values exceeding the HR values. This suggests that substantial unmeasured confounding would be required to negate the observed associations.
Discussion This 45-year follow-up study provides compelling evidence of the long-term association between high BP and stroke-related mortality. The findings highlight that both baseline BP and changes in BP over time are significant predictors of stroke-related death, with these associations being more pronounced in men. The study also sheds light on the complex pathways through which BP influences stroke-related mortality, with BMI acting as a mediator and gender as a moderator.
The results underscore the importance of BP control in reducing the risk of stroke-related death. Effective management of hypertension, particularly in men, could potentially mitigate the risk of stroke-related mortality. The mediating role of BMI suggests that interventions aimed at reducing BMI in individuals with high BP could further decrease the risk of stroke-related death.
Limitations While this study provides valuable insights, it has some limitations. The cohort was drawn from a specific population, which may limit the generalizability of the findings. Additionally, the study relied on self-reported data for some covariates, which could introduce recall bias. The lack of information on antihypertensive medication use is another limitation, as it may have influenced BP levels and the observed associations.
Conclusion This study demonstrates that high BP and persistent hypertension are significant risk factors for stroke-related mortality, with these associations being more pronounced in men. The findings also highlight the mediating role of BMI and the moderating role of gender in these associations. These results emphasize the importance of BP control and weight management in reducing the risk of stroke-related death, particularly in men.
doi.org/10.1097/CM9.0000000000001949
Was this helpful?
0 / 0