Objectives: To evaluate aldosterone and renin levels and aldosterone-to-renin ratios (ARRs) in young Indigenous and non-Indigenous adults in the Northern Territory, and their association with blood pressure levels.
Design: Cross-sectional study; single time point sub-study of two prospective birth cohort studies.
Setting, participants: Participants in the Aboriginal Birth Cohort (ABC) — born to Indigenous mothers at the Royal Darwin Hospital during 1987–1990 — and the Top End Cohort (TEC) — people born to non-Indigenous mothers in Darwin, recruited during 2007–2009 — aged 32–35 years at the time of this sub-study.
Main outcome measures: Plasma aldosterone and direct renin concentrations; ARRs (positive screening test result for primary aldosteronism defined as > 70 pmol/mU); systolic and diastolic blood pressure.
Results: A total of 255 ABC (205 in remote, 50 in urban locations) and 76 TEC members participated. Median aldosterone concentration was similar for all three groups. The median renin concentration was 7.5 mU/L (interquartile range [IQR], 4.1–12.4 mU/L) in the TEC group, 12.4 mU/L (IQR, 5.1–19 mU/L) in the urban ABC group, and 29.3 mU/L (IQR, 15.0–52.9 mU/L) in the remote ABC group. The median ARR was 10 pmol/mU (IQR, 6–19 pmol/mU) in the remote ABC group, 28 pmol/mU (IQR, 16–70 pmol/mU) in the urban ABC group, and 43 pmol/mU (IQR, 26–74 pmol/mU) in the TEC group. Thirteen urban ABC participants (26%), 21 TEC participants (28%), and six people in the remote ABC group (3%) had ARR values above 70 pmol/mU. Adjusted for age and body mass index (BMI), mean systolic and diastolic blood pressure were lower for women than men in all participant groups; after adjusting for age, sex, and BMI, larger ARR was associated with higher systolic blood pressure in the TEC group but not the two ABC groups.
Conclusion: Screening test results for primary aldosteronism were positive for about one-quarter of urban Indigenous and non-Indigenous participants. A prospective study that includes confirmatory testing would more accurately assess the prevalence of primary aldosteronism among Indigenous Australians in the Northern Territory.