People with high blood pressure may be at increased risk of developing brain tumours, new research has suggested.
Some 12 million people in the UK are diagnosed with high blood pressure while another 5.7 million are thought to have the condition but are unaware of it.
Experts analysed data for almost 580,000 people from Sweden, Austria and Norway, who were followed for around 10 years. Data on brain tumours was obtained from national cancer registries and, during follow-up, 1,312 brain tumours were diagnosed.
People were typically aged 41 at the start of the study and the typical age of diagnosis was 56 for a brain tumour. The most common tumours diagnosed were meningioma and glioma, which each account for around one third of all brain tumours.
Writing in the Journal of Hypertension, the experts said those 20% of participants with the highest blood pressure readings were more than twice as likely to later be diagnosed with meningioma or malignant glioma compared with the 20% with the lowest readings.
The study, by researchers from Austria, Norway and Sweden, was funded by World Cancer Research Fund.
Michael Edlinger, epidemiologist at the medical statistics department in Innsbruck in Austria and lead researcher of the study, said: "These results are interesting because the large number of people in this study and the fact that more than 1,000 of them developed brain tumours mean it is unlikely that the findings are down to chance.
"But this does not mean we can be confident that it is the high blood pressure that has caused the increase in brain tumour risk, as there are some limitations to our study. For example, we did not have data on whether the participants were using any medication, such as treatment for high blood pressure, which could have affected the results.
"And just like with the more speculative claims of mobile phone risks, we do not exactly know how such risks could work to cause the occurrence of these tumours. This is why more research is needed into whether high blood pressure increases risk of brain tumour."
Professor David Spiegelhalter of Cambridge University said: "It is important that the absolute risks are low: roughly two in 1,000 over 10 years for people with very low blood pressure, compared with three in 1,000 for those with high blood pressure. And people with high blood pressure are different in other ways: for example they are taking medication, and seeing doctors more, which may bring forward diagnosis of cancers."