Measuring and defining orthostatic hypotension in the older person

Estimates of the prevalence of orthostatic hypotension (OH) have previously found it to be as high as 6% in the community and 70% in long-term care facilities [1, 2]. Despite this high prevalence there remain many unanswered questions regarding the diagnosis, treatment and natural history of OH. The 1996 American Autonomic Society and American Academy of Neurology Consensus criteria were a big step forward in standardising the clinical diagnosis and enabling academic progress; defining OH by sphygmomanometric measured drops in systolic blood pressure (SBP) of 20 mmHg and diastolic blood pressure (DBP) of 10 mmHg during active standing or head up tilt [3]. Now these consensus criteria have been outgrown in many ways, largely as a result of the widespread use of continuous, beat-to-beat, non-invasive blood pressure monitoring. The 1996 diagnostic criteria appear too rigid for the dynamic profile gained during beat-to-beat monitoring. Commonly arising patterns for which the diagnostic criteria are unhelpful include brief but significant drops in BP and sustained BP drops that do not meet the diagnostic threshold. In an attempt to address these questions an update to the Consensus definition of OH was published in 2011 [2]. The specific changes include a definition for ‘initial OH’ (>40 mmHg drop SBP, >20 mmHg drop DBP), a requirement for a larger drop in people with hypertension (>30 mmHg SBP, but without a definition of what to consider as hypertension) and the addition of ‘sustained drop’ to our usual diagnostic criteria of OH (without a definition of what constitutes a sustained drop).