A South American tribe living in almost total isolation without Western dietary effects showed no increase in average blood pressure from age 1 to age 60, according to a study by researchers at the Johns Hopkins Bloomberg School of Public Health. For comparison, a nearby tribe whose diet includes several processed foods and salt showed higher blood pressure until late middle age.
In the United States and most other countries, blood pressure increases with age, starting early in life. The results of this study support the idea that the tendency in Western societies to increase blood pressure with age is not a natural part of aging, but may result from a cumulative effect of exposure to Western lifestyle and diet.
The findings appear on November 14 Cardiology of JAMA.
"The idea that raising blood pressure is the result of aging is a common belief in cardiology, but our findings add to the evidence that increased blood pressure may be the inevitable result of Western diet and lifestyle instead of aging itself," says Noel Miller, PhD, MPH, assistant professor of epidemiology at Bloomberg School And a member of the Walsh Center for Prevention, Epidemiology and Clinical Research.
For their study, the researchers took blood pressure measurements from 72 Yanomami ages 1-60, and found no trend towards higher or lower readings as participants aged. The researchers also measured blood pressure among the 83 members of the nearby Yakuana tribe, which was more exposed to Western influences, including nutrition – and here they found a clear upward trend in stress with advanced age.
Yanomami live as hunters-gatherers and gardeners in the remote rain forest of northern Brazil and southern Venezuela. Their diets are low in fat and salt and high in fruit and fiber. Studies of Yanomami for adults since 1980 have shown that atherosclerosis and obesity are virtually unknown among them, and that they have particularly low blood pressure on average, with no apparent increase with age.
The new study reveals that this stability of blood pressure among Yanomami begins in early childhood. This is the first to compare the Yanomami populations located in geographically shared – Yekwana – that have different exposure to Western diet and other Western lifestyle influences.
The researchers, who selected the members of Yanomami villages in southern Venezuela, found that their blood pressure measurements averaged 95 mm Hg and systolic over 63 diastolic. (In US adults, the average systolic is 122 and diastolic 71.) This low figure among rising Yanomami In line with previous Yanomami adult studies, but the researchers measured approximately the blood pressure among Yanomami children as well. In fact, the data indicate that the blood pressure in this population remained close to this low level from at least one age up to the age of 60, with no upward trend or decrease.
Unlike yanumi, hikuana was exposed to some aspects of western lifestyle and culture, including processed food, through interaction and trade with the industrialized world. While blood pressure readings at the youngest ages were almost identical to those of the age group, there was a clear trend towards an increase in levels with advanced age – about 0.25 mm Hg per year – so the yekuana had an average of 5.8 mm Hg higher in age 10, and 15.9 mm Hg higher at age 50.
"The increase in this age is linked to blood pressure at an early age, suggesting that early childhood may be a window of opportunity for lifestyle interventions to prevent the constant increase in blood pressure," says Miller.
To put these findings in context, systolic blood pressure in the US increases by about 1.5 mm Hg and 1.9 mm Hg per year for boys and girls respectively, and 0.6 mm Hg per year among adults.
Mueller and his colleagues plan to follow a study of the intestinal bacteria of Yanomami and Yekwana to determine whether the intestinal microbial account for two differences of blood pressure tribes with advanced age.
The funding was provided by the National Heart, Lung and Blood Institute (K01HL141589) Sloan, C & D Foundation and Emch Foundation for Microbial Diversity.