Abstract Body: Background The timing of orthostatic changes in blood pressure (BP) and their associations with orthostatic symptoms among very old adults is undercharacterized.

Objective To determine the prevalence of distinct orthostatic BP patterns and their relationships with orthostatic symptoms.

Methods We measured three supine and six standing BP readings (timed at 0, 1, 2, 3, 4, and 5 minutes after standing) among ARIC participants (2021-2023). OH patterns (primary, initial, early, delayed, and sustained) were based on when a drop in BP (systolic ≥20 or diastolic ≥10 mmHg) occurred (see Figure for definitions). We quantified OH prevalence overall and by anti-hypertensive medication use and determined the associations of OH patterns with orthostatic symptoms, both concurrent with positional change and in the prior 30-days via logistic regression adjusted for age, sex, and Black race.

Results Of 1,044 participants (58.8% female, 16.5% Black, mean age 83.9±3.7 years), 24.5% had primary OH. Initial and early OH were more common than sustained and delayed OH. Participants using any hypertension medications had a higher prevalence of most types of OH (Panel 1). Primary, early, and sustained OH were associated with orthostatic symptoms during the rise from supine to standing or when standing, while initial OH was associated with orthostatic symptoms only during the rise from supine to standing (Panel 2). Sustained OH was associated with higher odds of prior light-headedness or dizziness and early OH with higher odds of prior imbalance.

Conclusion Clinicians should consider timing of BP changes when screening for OH and evaluating its contribution to orthostatic symptoms among very old adults.