One-minute vs. three-minute assessment of orthostatic hypotension after standing may better predict adverse events, study suggests

Assessing orthostatic hypotension one minute after standing rather than the guideline-recommended three minutes may be a better predictor of adverse events, according to a recent study.

Researchers performed a prospective cohort study of participants in the Atherosclerosis Risk in Communities Study from 1987 to 1999 to compare the association of early versus late measurement of orthostatic hypotension with history of dizziness and adverse outcomes. Orthostatic hypotension, which was measured five times at 25-second intervals, was defined as a decrease in systolic blood pressure of at least 20 mm Hg or a decrease in diastolic blood pressure of at least 10 mm Hg from supine to standing position. The researchers examined the association of each of the five measurements with history of dizziness on standing and risk of falls, fracture, syncope, motor vehicle crashes, and all-cause mortality through Dec. 31, 2013. The study results were published online July 24 by JAMA Internal Medicine.

A total of 11,429 participants who had at least four measurements of orthostatic hypotension after standing were included in the study. Of these, 6,211 (54%) were women and 2,934 (26%) were black. Mean age was 54 years at baseline. Mean times after standing for measurements 1 through 5 were 28.0 seconds, 52.6 seconds, 76.4 seconds, 100 seconds, and 116.0 seconds, respectively. Only orthostatic hypotension at measurement 1 was associated with higher odds of dizziness (odds ratio, 1.49; 95% CI, 1.18 to 1.89); it was also associated with highest rates of fracture, syncope, and death (18.9 per 1,000 person-years, 17.0 per 1,000 person-years, and 31.4 per 1,000 person-years, respectively). Measurement 2 was associated with the highest rate of falls and motor vehicle crashes (13.2 per 1,000 person-years and 2.5 per 1,000 person-years, respectively). After adjustment, a significant association was seen between measurement 1 and risk of fall, fracture, syncope, and mortality and between measurement 2 and all long-term outcomes. For measurements performed after one minute, no association was seen with dizziness, and associations with long-term outcomes were not consistent.

The researchers noted that long-term outcomes were based on ICD-9 codes, hospital records, and CMS claims and that the protocol was designed to terminate when patients felt discomfort or became dizzy, among other limitations. However, they concluded that assessments of orthostatic hypotension within one minute of standing may be time-saving as well as the most clinically relevant and predictive of long-term prognosis. “These results represent compelling evidence for earlier time measurement in the assessment of [orthostatic hypotension] in middle-aged adults,” the authors wrote.

An accompanying editorial pointed out that each measurement had a 20/10 mm Hg cutoff and that changes outside this range were not examined. The cutoff applied even in patients with hypertension, for whom such variations may be considered in the normal range, the editorialists said. They also noted that the termination of the protocol at symptoms of discomfort or dizziness probably meant that patients with more severe orthostatic hypotension were not included.

However, they said the current study for the first time “provides unequivocal evidence of rather sinister implications” associated with milder forms of orthostatic intolerance and transient orthostatic hypotension. Because some patients do experience orthostatic decline in blood pressure that does not develop until they have been standing for three minutes, the editorialists recommended measuring blood pressure at both the one- and three-minute marks. Patients with otherwise unexplained abnormalities should be referred for formal autonomic testing, including “continuous beat-to-beat [blood pressure] recordings during supine rest and orthostasis, along with other means to assess autonomic nervous system function more formally and systematically,” the editorialists wrote.