Arterial Stiffness in Heart-Healthy Indigenous Tsimane Forager-Horticulturalists

Abstract

Background: Little is known about arterial stiffness in rural subsistence populations that experience few cardiovascular risk factors. We conducted a cross-sectional study comparing 3 arterial stiffness metrics among Tsimane forager-horticulturalists with 2 representative US cohorts.

Methods: Arterial elasticity (the inverse of stiffness) markers C1 (large artery elasticity) and C2 (small artery elasticity) were measured using a tonometry device among 490 Tsimane adults (mean age, 51.2±10.1 years; 55% women), and compared with 6294 multiethnic US adults (mean age, 62.0±10.2 years; 52% women) from MESA (Multi-Ethnic Study of Atherosclerosis). Carotid-femoral pulse wave velocity was assessed using the foot-to-foot method in a smaller Tsimane sample (n=94) and compared with 3086 predominantly White US adults (mean age, 46.1±8.7 years; 54% women) from the FHS Gen3 (Framingham Heart Study Third Generation).

Results: Tsimane participants exhibited superior arterial health compared with US cohorts, with higher elasticity (C1/C2) and lower stiffness (carotid-femoral pulse wave velocity). Their C1 (mean 22.8±12.2 mL/mm Hg×10) and C2 (mean 7.5±4.0 mL/mm Hg×100) were 47.3% and 35.7% higher than MESA participants by age 40 years, respectively, and differences remained sustained throughout adulthood. Compared with participants in FHS Gen3, the carotid-femoral pulse wave velocity in Tsimane participants (mean 6.2±1.2 m/s) was 33.9% lower and showed a minimal age-related increase, with carotid-femoral pulse wave velocity only higher by age 70+ (β=1.74±0.38; reference <40 years). Tsimane participants with ≥2 comorbidities (hypertension, obesity, and diabetes) had ≈25% higher arterial elasticity than healthy Americans with no comorbidities.

Conclusions: Tsimane forager-farmers of the Bolivian Amazon demonstrate substantially lower arterial stiffness throughout adulthood than more urbanized and sedentary populations, and the differences are only partially explained by conventional cardiometabolic risk factors.

Keywords: arterial stiffness; cardiovascular health; indigenous health; vascular aging.

Figure 1. C1, C2, and cfPWV stiffness levels by age.

Shown are the adjusted C1 (A), C2 (B), and cfPWV (C) levels among age groups in 10‐year intervals. Predicted values of C1 and C2 were obtained from multivariable linear regression models adjusting for sex, height, BMI, heart rate, SBP, DBP, fasting glucose, triglycerides, LDL‐C, HDL‐C, and an interaction term reflecting ethnicity × age group. Predicted cfPWV was obtained from a similar model adjusting for sex, height, BMI, heart rate, SBP, DBP, and an interaction term reflecting cohort × age group. Points are mean values, and error bars show 95% CIs. BMI indicates body mass index; C1, large artery elasticity; C2, small artery elasticity; cfPWV, carotid‐femoral pulse wave velocity; DBP, diastolic blood pressure; FHS Gen3, Framingham Heart Study Third Generation; HDL‐C, high‐density lipoprotein cholesterol; LDL‐C, low‐density lipoprotein cholesterol; and SBP, sytolic blood pressure.

Figure 2. Association of age with C1, C2, and cfPWV.

Shown are the estimated effects (β value, difference in elasticity unit per year) of age on C1 (A), C2, (B), and cfPWV (C) in model 1, model 2, and model 3. Model 1 was the unadjusted model. Model 2 was adjusted for sex, height, BMI, heart rate, SBP, and DBP. Model 3 was further adjusted for fasting glucose, triglycerides, LDL‐C, and HDL‐C. Lipid data are missing in the cfPWV data set and thus were not analyzed. Points are estimated effect sizes (β value), and error bars show 95% CIs. The dashed vertical line indicates x=0. All R ² values were highly significant (P<0.001). Units of β: C1 (mL/mm Hg×10), C2 (mL/mm Hg×100), and cfPWV (m/s). BMI indicates body mass index; C1, large artery elasticity; C2, small artery elasticity; cfPWV, carotid‐femoral pulse wave velocity; DBP, diastolic blood pressure; FHS Gen3, Framingham Heart Study Third Generation; HDL‐C, high‐density lipoprotein cholesterol; LDL‐C, low‐density lipoprotein cholesterol; and SBP, systolic blood pressure.

Figure 3. C1 and C2 levels by comorbidity status.

Shown are the levels of C1 (A) and C2 (B) across cardiometabolic comorbidity status in each ethnicity subset. Estimated C1 and C2 values were derived from multivariable linear regression models adjusted for age, sex, heart rate, triglyceride, LDL‐C, and HDL‐C. C1 indicates large artery elasticity; C2, small artery elasticity; HDL‐C, high‐density lipoprotein cholesterol; and LDL‐C, low‐density lipoprotein cholesterol.

Figure 4. A teenage girl sifts rice after pounding it to separate the husk from the grain (A), a group of men embark on a multiday hunting trip (B), 2 sisters and their children harvest sweet manioc roots with machetes and knives (C), and an older man chops firewood for cooking (D).

Photo credits: Michael Gurven.