To assess the association between 24 hours urinary sodium and potassium excretion with blood pressure (BP) in rural and urban pygmies and Bantus of southern Cameroon.Design and method:
In this cross-sectional survey, we compared 100 traditional pygmies (TP) living in equatorial forest (Lolodorf) and their 100 neighbors traditional Bantus (TB) living in Bidjouka village, to 100 contemporary pygmies (CP) and 100 contemporary Bantus (CB) both living in urban environment in Kribi city. Trained observers recorded in each participant lifestyle and socio-demographic data, height, weight, waist circumference, blood pressure (BP), and 24 hours urine specimen. Brachial systolic BP (SBP) and diastolic BP (DBP) were measured in triplicate using an automatic sphygmomanometer (Omron 705 CP). The urinary sodium (UNaC) and potassium (UKC) concentration was determined by flame photometry.Results:
Pygmies were younger than Bantus: mean age = 38 ± 16 vs 45 ± 17 years, p = 0.0001. UNaC and UKC were lower in Pygmies than in Bantus (1.91 ± 1.27 g/l vs 2.31 ± 1.11 g/l, and 2.33 ± 1.55 vs 2.65 ± 1.54, respectively, both p < 0.05). UNaC was similar within Pymy and Bantu groups. By contrast, UKC was higher in TP than CP (2.60 ± 1.1 vs 2.06 ± 1.34 g/l, p = 0.013), and in TB than CB (2.98 ± 1.64 vs 2.30 ± 1.34, p = 0.002). Age-adjusted SBP and DBP were lower in pygmies than in Bantus (both P < 0.0001), but were similar between TP and CP. UNaK > 2 g/l significantly increased SBP and DBP in the whole study population and in Bantus (all p < 0.01), but not in Pygmies. Age-adjusted prevalence of hypertension was lower in TP than in CP (4% vs 11%) and in TB compared with CB (19% vs 24%). Multivariate logistic regression model revealed that urban environment, increased age, abdominal obesity, UNaC, and sodium-to-potassium ratio were independent determinants of hypertension in Bantus (all p < 0.05), while increased age and urban environment were independently associated with hypertension in Pygmies (both p < 0.05).Conclusions:
This study reveals that hunter-gatherer lifestyle is associated with low UNaC and high UKC which likely explain the lower prevalence of hypertension in Pygmies. Hypertension is more common in Bantus, mostly driven by unhealthy behaviours with high salt diet.