By AMERICAN HEART ASSOCIATION NEWS
Scientists say there are indications of a potentially dangerous link between high rates of malaria and high blood pressure, and they are urging more research in hopes of better addressing harmful effects of hypertension in malaria –stricken areas.
A paper by researchers in Africa and the United Kingdom said there is reason to believe malaria and high rates of high blood pressure are linked in low- to medium-income countries — even among children.
That’s especially true in sub-Saharan Africa, where the infectious disease is so common and blood pressure levels are often high, the researchers wrote in the paper released Thursday in Circulation Research.
The paper’s lead author Anthony O. Etyang, M.D., a consultant physician and clinical scientist at the KEMRI-Wellcome Trust Research Programme, in Kilifi, Kenya, Africa, said the association makes sense for several reasons.
One is blood pressure tends to be high in parts of the world where malaria, a mosquito-borne infectious disease, causes flu-like symptoms, is prevalent.
Malaria can be deadly for those who aren’t treated. According to the Centers for Disease Control and Prevention, in 2015, there were an estimated 214 million malaria cases worldwide and 438,000 people died. Most of the dead were children in Africa.
Etyang said a second reason to believe there is an association is that malaria in pregnancy causes low birth weight, which has been shown in studies to be associated with the development of high blood pressure later in life.
Research published in Hypertension in January 2014 suggests that, in Nigeria, children born of mothers who suffered malaria tend to have higher blood pressures at 1 year of age.
“Because blood pressure patterns tend to be sustained over the course of time, these children are more likely to become hypertensive as adults,” Etyang said.
Yet another reason for the potential association, he said, is that malaria in childhood causes malnutrition and, especially, stunting.
“Malnutrition and stunting in childhood have also been shown in developed countries to predispose individuals to developing hypertension,” Etyang said.
In addition, he said, malaria in childhood causes inflammation, which, in turn, can lead to arterial stiffness and high blood pressure.
To test the hypothesis, convince others and encourage more research, the study authors reviewed scientific studies on high blood pressure and checked those that might also be associated with malaria.
They came up with different types of research that could reveal whether there is an association, including ecological studies, in which researchers would look at the distribution of a disease on a map and overlay it against the distribution of another disease or exposure to see if the two could be related.
They could do cohort studies, in which they would follow up with people for a long time to see if the subjects developed a particular disease. And they suggest Mendelian randomization studies, which use the backdrop of genetics to determine the contribution of environmental factors to disease development.
“If this link exists then it would be a game-changer in understanding malaria and hypertension. It might be possible to develop drugs that target the pathways activated by malaria that lead to hypertension. These drugs would be of great use in sub-Saharan Africa,” Etyang said.
It’s possible that if malaria causes high blood pressure, many other infectious diseases also could lead to hypertension, according to Etyang.
“Further research would be needed to see if factors arising during infectious episodes that lead to hypertension could be identified and treated along with the infection to prevent future adverse consequences,” he said. “Also, if this link exists, it would increase the economic benefit of eliminating malaria.”
High cardiovascular disease rates are indeed an area that needs more attention in low- and middle-income countries, and high blood pressure could be a main contributor to cardiovascular disease risk, according to Roger Bedimo, M.D., chief of the infectious diseases section at VA North Texas Health Care System and associate professor of medicine at UT Southwestern Medical Center.
But, Bedimo, who wasn’t among the researchers on the new paper, said he isn’t as confident there is a link between malaria and hypertension.
While it’s possible that malaria-induced low-birth weight will later lead to hypertension in adulthood, malnutrition from malaria infestation would predispose to hypertension later in life, and malaria-induced chronic inflammation would be a risk factor for cardiovascular disease, Bedimo said that he believes there are other, potentially better, explanations for high rates of hypertension in low- and middle-income countries.
“Behavioral factors such as salt consumption, which is rather liberal in many [low- and middle-income countries], would be a far more proximate cause of hypertension,” Bedimo said. “Should malaria indeed be associated with hypertension, there could be a rather more direct explanation that would need to be explored first, [such as] anemia.
“Anemia is a very frequent complication of malaria in endemic areas. Chronic anemia is, itself, a proven risk factor for enlarged heart and could well more directly predispose to hypertension,” he said.