Chronically high blood pressure is a serious health problem that affects about one out of every three adults and contributes to approximately 17.5 million deaths worldwide each year. While there are many things people can do to try to keep their blood pressure down — lower salt intake, maintain a healthy weight and drink in moderation — studies have shown that genetics also plays a part.
But finding common genetic variations that affect blood pressure hasn’t been easy. Just five months ago The Blog reported on the first validated association in Europeans. Now, two large consortia have identified several more. Their findings, published online this week in the journal Nature Genetics, expand the current understanding of how blood pressure is determined and may point the way towards targets for new drugs for treating possibly preventing hypertension.
“None of the genes we identified as having common variation are part of the system we know about that regulates blood pressure — the genes identified are not the ones targeted by current prescription drugs to control hypertension. If we can increase the number of genes implicated in blood pressure maintenance…our understanding of the biology will change completely,” said Aravinda Chakravarti, head of the Center for Complex Disease Genomics in the McKusick-Nathans Institute of Genetic Medicine at Johns Hopkins University School of Medicine and a co-author of one of the studies, in a statement.
The two research groups analyzed data from an enormous number of people — more than 50,000 in the Global BPgen study and more than 29,000 in the CHARGE study. Such large samples are needed because variation in blood pressure is likely due to many variations, each with very small effects.
After conducting their own analyses, the researchers from each consortium shared their findings with each other, allowing the scientists to further confirm their results. Altogether, six distinct variations associated with systolic blood pressure (SBP) and nine associated with diastolic blood pressure (DBP) were found and confirmed between the two studies. The Global BPgen consortium also studied more than 12,000 South Asian Indians and found evidence for an association between blood pressure and two of the SNPs identified in the European studies.
Further analysis of the Global BPgen results showed that all of the SNPs associated with SBP through the genomewide analysis were similarly related to DBP, and vice versa. And not surprisingly, all of the SNPs the researchers identified were also associated with hypertension; the version of each SNP linked to lower blood pressure was also decreased a person’s odds of having the condition.
The effects of the individual SNPs were small, but the authors of both studies point out that small changes in blood pressure can translate to important changes in the risk of heart disease and stroke. For example, the authors of Global BPgen study say that lowering SBP by 2 mmHg has been estimated to translate into 6% lower risk of stroke and 5% lower risk of coronary heart disease. The authors of the CHARGE study cite other data showing that a prolonged increase in DBP of 5 mm Hg is associated with a 34% increase in risk for stroke and a 21% increase in the risk of coronary events.