Among 3,966 patients with confirmed primary aldosteronism (PA) in a 14,750-patient hypertensive cohort, the share testing below the conventional aldosterone-to-renin ratio (ARR) cutoff of 20 fell steadily with age: 57.5% under age 35, 50.6% at 35-44, 35.4% at 45-54, and 33.2% at 55 and older. Each added year of age cut the odds of a sub-20 ARR by about 2.5% (adjusted OR 0.975), even after excluding adrenal nodules, low potassium and reduced kidney function. Younger patients' renin activity was relatively preserved.
This matters because PA is the most common secondary cause of hypertension and carries excess stroke, atrial fibrillation and kidney risk beyond what blood pressure alone explains, yet it is notoriously under-diagnosed. Renin declines with age, mechanically inflating ARR in older patients and deflating it in younger ones, so a single cutoff behaves differently across decades. The practical message: a young adult with early-onset or resistant hypertension and a 'negative' ARR may still warrant confirmatory testing, and aldosterone and renin deserve review individually, not just as a ratio. Key caveats: this is a retrospective single-region study in a specialist center, where referral bias is likely, since patients with ARR below 20 only reached saline testing when suspicion was high. Confirmatory testing also has imperfect accuracy, and no outcomes data show that detecting these cases improves prognosis. Confirmatory rather than paradigm-shifting, it reinforces calls for age-adjusted PA screening, and adults with hypertension onset before 40 can reasonably raise it with their physician.