Researchers at Oxford Population Health have found new evidence in data collected by the China Kadoorie Biobank on the optimum levels of blood pressure for the prevention of stroke and coronary heart disease.
The results demonstrated that a person could still be at risk of both stroke and coronary heart disease even if their systolic blood pressure (pressure in their arteries when their heart beats) is well below the threshold of 140 mmHg, which is conventionally used to determine whether or not a person needs to start blood pressure-lowering medication. The study is published in Hypertension.
Previous observational studies have demonstrated that mean levels of systolic blood pressure increase with age and the risks of vascular disease outcomes also increase with higher levels of systolic blood pressure. In this study, researchers in Oxford and China used a Mendelian randomisation analysis to compare the risk associations between systolic blood pressure and cardiovascular and non-cardiovascular disease in 489,495 adults whose data were collected by the China Kadoorie Biobank, which also includes genetic data from 86,060 participants.
Mendelian randomisation studies can help us to understand how differences in our genes linked to systolic blood pressure can affect our likelihood of suffering a stroke or heart attack more accurately than observational analyses, which can be influenced by reverse causality whereby blood pressure drops after the onset of disease.
- Higher levels of genetically-predicted systolic blood pressure were associated with higher risks of all vascular disease types, at each level of systolic blood pressure down to 120 mmHg.
- For every 10 mmHg increase in genetically-predicted systolic blood pressure above 120 mmHg, a person’s relative risk of experiencing intra-cerebral haemorrhage was 2-fold greater than for either ischaemic stroke or major coronary events.
- Likewise, the relative risks for vascular disease per 10 mmHg higher genetically-predicted blood pressure for vascular disease were 2-fold greater in younger than in older people, but the absolute risks for vascular disease are far greater at older ages.
- In contrast with observational analyses, the associations of genetically predicted systolic blood pressure with diabetes or chronic kidney disease were not statistically significant.
Robert Clarke, Professor of Epidemiology and Public Health Medicine at Oxford Population Health, and lead author of the study, said ‘These results provide support for strategies and treatments aimed at lowering systolic blood pressure down to 120 mmHg in a wider range of the population for prevention of major cardiovascular diseases, which in turn could prevent millions of premature deaths and reduce disability due to the non-fatal cardiovascular disease events that would be avoided.’
Sarah Parish, Professor of Medical Statistics and Epidemiology, said ‘The novel genetic findings demonstrated no evidence of any hazards for major disease outcomes at lower levels of systolic blood pressure down to 120 mmHg, suggesting that it is both safe and beneficial to reduce the targets for lowering blood pressure to prevent the onset of cardiovascular disease in high risk individuals.’
Read more in the commentary on this article, Systolic Blood Pressure and Cardiovascular Risk: Straightening the Evidence.