A South American tribe living in almost total isolation with no Western dietary influences showed no increase in mean blood pressure between ages 1 and 60, according to a study conducted by researchers at the Johns Hopkins School of Public Health Bloomberg . In comparison, a nearby tribe, whose diet includes some processed foods and salt, showed higher blood pressure in late middle age.
In the US and most other countries, blood pressure increases with age, starting early in life. The results of this study support the view that the trend in Westernized blood pressure societies to increase with age is not a natural part of aging, but may result from a cumulative effect of exposure to western diet and lifestyle.
The results appear November 14 in the journal JAMA Cardiology.
"The idea that increasing blood pressure is a result of aging is a widely held belief in cardiology, but our findings add to evidence that increased blood pressure may be an avoidable consequence of western diet and lifestyle," says Noel Mueller. PhD, MPH, assistant professor of epidemiology at Bloomberg School and a member of the Welch Center for Prevention, Epidemiology and Clinical Research.
For the study, the researchers conducted blood pressure measurements of 72 Yanomami aged between 1 and 60 years, and found no tendency for major or minor readings as the participants aged. The researchers also measured blood pressure in 83 members of the neighboring Yekwana tribe, which is more exposed to western influences, including diet – and here they have discovered a clear tendency to increase pressure with advancing age.
The Yanomami live as hunter-gatherers and gardeners in a remote rainforest region in northern Brazil and southern Venezuela. Their diet is low in fat and salt and high in fruits and fiber. Studies with Yanomami adults since the 1980s have shown that atherosclerosis and obesity are virtually unknown among them, and they have remarkably low blood pressure, on average, with no apparent increase as they age.
The new study reveals that this age-stability of blood pressure among the Yanomami begins in early childhood. It is the first to compare the Yanomami to a geographically localized population – the Yekwana – which had a different exposure to the Western diet and other influences of the Western lifestyle.
The researchers, examining members of Yanomami villages in southern Venezuela, found that blood pressure measurements averaged 95 (mm Hg) systolic above 63 diastolic. (In American adults, systolic mean is 122 and diastolic is 71.) This low number among the Yanomami is consistent with previous studies in Yanomami adults, but the researchers measured approximately the same blood pressure among Yanomami children. In fact, the data suggest that blood pressure in this population remains close to the same low level, from one year to at least 60 years, with no tendency to increase or decrease.
In contrast to the Yanomami, the Yekwana were exposed to some aspects of the western diet and lifestyle, including processed foods, through interaction and trade with the industrialized world. Although blood pressure readings at younger ages were virtually the same for their Yanomami pairs, there was a statistically clear trend of increasing levels with advancing age – about 0.25 mm Hg per year – such that Yekwana had mean levels of 5.8 mm Hg higher at 10 years and 15.9 mm Hg higher at 50 years.
"This age-related blood pressure increase begins in early childhood – suggesting that early childhood may be a" window of opportunity "for lifestyle interventions to prevent increased blood pressure," he says. Mueller.
To put these findings in context, in the U.S. systolic blood pressure increases about 1.5 mmHg and 1.9 mmHg per year between boys and girls, respectively, and 0.6 mmHg per year among adults.
Mueller and his colleagues plan to follow a study of the intestinal bacteria of the Yanomami and Yekwana to determine if the intestinal microbiome responds by differences in blood pressure between the two tribes as the age advances.
Funding was provided by the National Heart, Lung and Blood Institute (K01HL141589), the Alfred P. Sloan Foundation, the C & D Fund, and the Emch Fund for Microbial Diversity.