It is a disease which afflicts about one billion people across the globe. Now a chance discovery by a team of Chinese doctors has shed new light on the possible cause of high blood pressure - and even the possibility of a vaccine.
The team from the Beijing Chaoyang Hospital's Cardiology Centre have found a correlation between infection by a common virus and high blood pressure, or hypertension - a finding that may overturn the conventional understanding of the disease.
The virus at the centre of the research is human cytomegalovirus (HCMV). HCMV is a common virus that infects most people at some time during their lives but rarely causes obvious illness.
Research team leader Dr Yang Xinchun said that it was in 2009 that they accidentally discovered that the levels of hcmv-miR-UL112, a type of microRNA generated after contracting HCMV, was three times higher in people with hypertension than those without.
That result, from a small testing group involving just 13 high blood pressure patients and five healthy ones, prompted the doctors to look more closely.
'There are some other types of microRNA related with the HCMV, and some other researchers have done experiments in exploring the connection between them and hypertension,' Yang said. 'But for miR-UL112, there was no research. Therefore, we decided to head our research towards this direction.'
In a larger-scale screening held last year, the levels of hcmv-miR-UL112 in 197 hypertension patients was found to be 2.52 times that of 97 people without high blood pressure.
Researchers also found that when tested for HCMV, 52.7 per cent of hypertension patients were positive, compared with 30.9 per cent of those without hypertension. in the group.
Furthermore, the titers - a measurement of the concentration of the virus - was found to be 30 times greater in hypertension patients than those without high blood pressure.
Yang said the team also carried out laboratory experiments and for the first time found that miR-UL112 could increase the volatility of blood pressure, through inhibiting the expression of IRF-1, an interferon regulatory factor. It can also survive in the body after curbing the function of an immune system molecule named MICB.
Dr Cai Jun, another of the research paper's authors, said the team's next step was to check the cause-and-effect relationship between the HCMV and hypertension by studying 2,000-3,000 people over the next two to five years.
'There is a big gap from our current observation of their correlation and confirming that the disease is caused by the virus,' Cai said.
Dr Ricky Man, professor of pharmacology and pharmacy at the University of Hong Kong, described the research by the Beijing team as a 'very interesting study'.
'These investigators have pointed out that much work is needed to demonstrate how the cytomegalo- virus infection produces hypertension,' he said.
'Another important aspect is to demonstrate if controlling the infection, perhaps by antiviral medications, can reverse or reduce hypertension.'