Association of urinary sodium excretion with blood pressure and risk factors associated with hypertension among Cameroonian pygmies and bantus: a cross-sectional study

Abstract

Background: High salt intake increases blood pressure (BP) and hypertension risk. This study aimed to examine association of urinary sodium excretion with BP and hypertension correlates among Cameroonian pygmies under hunter-gatherer subsistence mode and Bantus, living in urban area under unhealthy behavioral habits.

Methods: In this cross-sectional cluster sampling study, we randomly enrolled rural pygmies living in Lolodorf and urban Bantus living in Douala. The World Health Organization steps questionnaire was used to collect socio-demographic and lifestyle data. Height, weight, BP and single overnight spot urine samples were obtained in all participants. BP was measured in triplicate. Urinary sodium and potassium excretion was determined by flame photometry. Data were recorded and analyzed using SPSS 16.0.

Results: We included 150 Pygmies and 150 Bantus aged 38 ± 12 years and 33 ± 11 years, respectively (p < 0.0001). Compare to Bantus, pygmy's height and weight were respectively: 1.54 ± 0.09 m vs 1.72 ± 0.12 m; and 54.4 ± 9.2 kg vs 77.2 ± 14.8 kg, all p < 0.0001. Age-standardized prevalence of hypertension was 3.3% among Pygmies and 28% among Bantus (p < 0.0001). Age-adjusted systolic and diastolic BP were lower in Pygmies than in Bantus (107 ± 12 vs 119 ± 17 mmHg and 71 ± 11 vs 78 ± 13 mmHg respectively, all P < 0.0001). BP increased with age but to a lesser extent in Pygmies (all p < 0.01). Urinary sodium excretion was lower in Pygmies than in Bantus (46.9 ± 32.4 vs 121.5 ± 61.0 mmol/l, p < 0.0001). Systolic and diastolic BP were positively associated with urinary sodium excretion in Bantus (all p < 0.05). In the two groups, urinary potassium excretion was similar, and was not related to blood pressure. In the total study group and in Bantus taken separately, urinary sodium excretion was higher in hypertensive than in normotensive subjects. Multivariable logistic regression showed that urinary sodium excretion, Bantu status and age emerged as independent determinants of hypertension in the whole study group (OR (95%CI): 1.012 (1.005-1.018); 11.408 (3.599-36.165); 1.095 (1.057-1.135) respectively, p < 0.0001).

Conclusion: Hunter-gatherer pygmies exhibit low level of urinary sodium excretion related to low rate of hypertension and slower BP increase with age. Salt intake was a major driver of hypertension in our study population. Our findings highlight the need of efforts to implement nationwide prevention programs promoting risk factor screening and healthier lifestyles including reduction of dietary salt intake in Cameroonian.

Keywords: Bantu; Blood pressure; Hunter-gatherer lifestyle; Hypertension; Pygmy; Urinary sodium excretion.

Fig. 1

Linear regression of Systolic blood pressures (SBP), Diastolic blood pressure (DBP), Mean blood pressure (MBP) and Pulse pressures (PP) with aging. r represents linear regression coefficient

Fig. 2

Comparison of urinary sodium between hypertensive and normotensive participants. The midline of the boxes represents the median and the lower and upper margins represent the 25th and 75th percentiles, respectively. The lower and upper ends represent the minimum and maximum values respectively