Hemoglobin and ferritin concentrations are positively associated with blood pressure and hypertension risk in older adults: a retrospective cross-sectional study, Sharpeville, South Africa

Background and Objectives: We aimed to determine the association between Hemoglobin (Hb) and ferritin with blood pressure (BP) and risk of hypertension (HTN) among elderly South African adults in four time points over a period of 10 years. Methods and Study Design: We used the data source from the Sharpeville Project conducted among the elderly in Sharpeville, South Africa (SA). A total of 275 subjects from the 2004 data source were included. Among these, data were available for 251, 114, and 81 subjects in 2007, 2012, and 2014 respectively. Confounding factors included age, BMI, sodium intake, high-sensitivity C-reactive protein (hs-CRP), and serum total cholesterol. Linear and logistic regressions were used to investigate the Hb and ferritin associations with BP and HTN risk. Results: Mean age in 2004, 2007, 2012, and 2014 was 72.8 +/- 8.66, 75.8 +/- 7.28, 80.2 +/- 9.54, and 83.2 +/- 8.98 respectively. In the unadjusted model, systolic BP (SBP) and diastolic BP (DBP), after 132.2 and 83.6 mmHg, increased by 0.57 and 0.72 mmHg respectively for each increment increase in Hb. In the adjusted model, slope coefficients remained statistically significant. Adjusted OR (95% CI) for the highest quartile of Hb (Q4) compared to the first quartile (Q1) in 2004 (p<0.001) and 2007 (p=0.017) were 2.81(2.12-4.83) and 2.58 (1.18-5.65) respectively. Those in Q4 of ferritin had OR (95% CI) of 1.85(1.32-3.73) in 2004 (p<0.001) and 2.20 (1.24-4.04) in 2007 (p<0.001) compared to Q1. Conclusions: Consistencies between the results from both variables suggest that some part of these positive associations could be iron dependent. Caution should be taken about unmonitored iron supplements consumption among older adults particularly those with elevated BP or on antihypertensive medications.