Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study

Abstract

Background: Conventional coronary artery disease risk factors might potentially explain at least 90% of the attributable risk of coronary artery disease. To better understand the association between the pre-industrial lifestyle and low prevalence of coronary artery disease risk factors, we examined the Tsimane, a Bolivian population living a subsistence lifestyle of hunting, gathering, fishing, and farming with few cardiovascular risk factors, but high infectious inflammatory burden.

Methods: We did a cross-sectional cohort study including all individuals who self-identified as Tsimane and who were aged 40 years or older. Coronary atherosclerosis was assessed by coronary artery calcium (CAC) scoring done with non-contrast CT in Tsimane adults. We assessed the difference between the Tsimane and 6814 participants from the Multi-Ethnic Study of Atherosclerosis (MESA). CAC scores higher than 100 were considered representative of significant atherosclerotic disease. Tsimane blood lipid and inflammatory biomarkers were obtained at the time of scanning, and in some patients, longitudinally.

Findings: Between July 2, 2014, and Sept 10, 2015, 705 individuals, who had data available for analysis, were included in this study. 596 (85%) of 705 Tsimane had no CAC, 89 (13%) had CAC scores of 1-100, and 20 (3%) had CAC scores higher than 100. For individuals older than age 75 years, 31 (65%) Tsimane presented with a CAC score of 0, and only four (8%) had CAC scores of 100 or more, a five-fold lower prevalence than industrialised populations (p≤0·0001 for all age categories of MESA). Mean LDL and HDL cholesterol concentrations were 2·35 mmol/L (91 mg/dL) and 1·0 mmol/L (39·5 mg/dL), respectively; obesity, hypertension, high blood sugar, and regular cigarette smoking were rare. High-sensitivity C-reactive protein was elevated beyond the clinical cutoff of 3·0 mg/dL in 360 (51%) Tsimane participants.

Interpretation: Despite a high infectious inflammatory burden, the Tsimane, a forager-horticulturalist population of the Bolivian Amazon with few coronary artery disease risk factors, have the lowest reported levels of coronary artery disease of any population recorded to date. These findings suggest that coronary atherosclerosis can be avoided in most people by achieving a lifetime with very low LDL, low blood pressure, low glucose, normal body-mass index, no smoking, and plenty of physical activity. The relative contributions of each are still to be determined.

Funding: National Institute on Aging, National Institutes of Health; St Luke's Hospital of Kansas City; and Paleocardiology Foundation.

Figure 1

Study profile ^*Data were missing mainly because of broken laboratory equipment, electricity issues, missing supplies, or absent or sick laboratory personnel; data were missing for blood biomarkers, cholesterol, body fat, and confidence in the validity of the age estimate.

Figure 2

CAC scores by age for US MESA, and Tsimane samples Tsimane have significantly lower CAC for each age category (all p ≤0.0001). Raw data and t tests for differences between Tsimane and MESA are given in the appendix. Error bars show 95% CI. CAC=coronary artery calcium.

Figure 3

CAC score by age and CAC percentile in MESA white men (A) and Tsimane men (scaled to MESA men at 0-4800; B) and in MESA white women (C) and Tsimane women (D) and Tsimane men (scaled to MESA women at 0-1600; E) Raw Tsimane data in five percentile groups for each age group are in the appendix. MESA=Multi-Ethnic Study of Atherosclerosis. CAC=coronary artery calcium.

Figure 4

75th percentile of CAC score in women (A) and men (B) across populations Data sources are in the appendix. Data were used from the Heinz Nixdorf RECALL Study (HNR), the Multi-Ethnic Study of Atherosclerosis (MESA),^-, Japan, the Mid America Heart Institute (MAHI), the University of Illinois at Chicago, and Korea. A bootstrapped 95% CI is displayed for the Tsimane data. CAC=coronary artery calcium.

Figure 5

An extended Tsimane family at the entrance to their home (A), two sisters and their children harvesting manioc root (B), a man and his son fishing with bow and arrow (C), and two men butchering a deer after hunting in the forest (D)