Association of History of Dizziness and Long-term Adverse Outcomes With Early vs Later Orthostatic Hypotension Assessment Times in Middle-aged Adults.

Importance: Guidelines recommend assessing orthostatic hypotension (OH) 3 minutes after rising from supine to standing positions. It is not known whether measurements performed immediately after standing predict adverse events as strongly as measurements performed closer to 3 minutes. Objective: To compare early vs later OH measurements and their association with history of dizziness and longitudinal adverse outcomes. Design, Setting, and Participants: This was a prospective cohort study of middle-aged (range, 44-66 years) participants in the Atherosclerosis Risk in Communities Study (1987-1989). Exposures: Orthostatic hypotension, defined as a drop in blood pressure (BP) (systolic BP ≥20 mm Hg or diastolic BP ≥10 mm Hg) from the supine to standing position, was measured up to 5 times at 25-second intervals. Main Outcomes and Measures: We determined the association of each of the 5 OH measurements with history of dizziness on standing (logistic regression) and risk of fall, fracture, syncope, motor vehicle crashes, and all-cause mortality (Cox regression) over a median of 23 years of follow-up (through December 31, 2013). Results: In 11 429 participants (mean age, 54 years; 6220 [54%] were women; 2934 [26%] were black) with at least 4 OH measurements after standing, after adjustment OH assessed at measurement 1 (mean [SD], 28 [5.4] seconds; range, 21-62 seconds) was the only measurement associated with higher odds of dizziness (odds ratio [OR], 1.49; 95% CI, 1.18-1.89). Measurement 1 was associated with the highest rates of fracture, syncope, and death at 18.9, 17.0, and 31.4 per 1000 person-years. Measurement 2 was associated with the highest rate of falls and motor vehicle crashes at 13.2 and 2.5 per 1000 person-years. Furthermore, after adjustment measurement 1 was significantly associated with risk of fall (hazard ratio [HR], 1.22; 95% CI, 1.03-1.44), fracture (HR, 1.16; 95% CI, 1.01-1.34), syncope (HR, 1.40; 95% CI, 1.20-1.63), and mortality (HR, 1.36; 95% CI, 1.23-1.51). Measurement 2 (mean [SD], 53 [7.5] seconds; range, 43-83 seconds) was associated with all long-term outcomes, including motor vehicle crashes (HR, 1.43; 95% CI, 1.04-1.96). Measurements obtained after 1 minute were not associated with dizziness and were inconsistently associated with individual long-term outcomes. Conclusions and Relevance: In contrast with prevailing recommendations, OH measurements performed within 1 minute of standing were the most strongly related to dizziness and individual adverse outcomes, suggesting that OH be assessed within 1 minute of standing.