Orthostatic hypotension (OH) and mortality in relation to age, blood pressure and frailty
Introduction
OH is a common problem in older adults (Gupta and Lipsitz, 2007, Kearney and Moore, 2009), especially those admitted to hospital. Often seen with systolic hypertension (Gangavati et al., 2011), OH can also occur in the absence of frank cardiovascular disease (Robertson, 2008). In both settings, it is associated with a variety of adverse health outcomes (Gupta and Lipsitz, 2007). In consequence, the measurement of orthostatic change in blood pressure is a common practice in geriatric medicine. By long convention, OH is operationalized as either a >20 mmHg drop in systolic blood pressure and/or a >10 mmHg drop in diastolic blood pressure within 3 min of standing (The Consensus Committee of the American Autonomic Society and the American Academy of Neurology, 1996, Freeman et al., 2011). Clinical experience suggests that, as with other performance measures (Rockwood et al., 2007), OH is commonly infeasible for clinicians to measure in people who are ill or who have balance problems. In consequence, OH commonly goes undetected.
As with OH, frailty is also understood to be important and to increase with age, and its measurement can also vary. In general, frailty represents the differential vulnerability to adverse outcomes of people of the same chronological age (Abellan van Kan et al., 2010). Two poles are described in frailty operationalization. On the one hand, frailty is commonly described as a physical syndrome, with five specific characteristics (slow mobility, impaired grip strength, reduced activity, weight loss, exhaustion) contributing to what is described as a phenotype of frailty (Fried et al., 2001). On the other hand, frailty can be considered in relation to the accumulation of deficits, with little restriction as to what is considered as a deficit as long as a sufficient number of deficits are measured (Mitnitski et al., 2001). In population studies, some degree of deficit accumulation occurs before the frailty phenotype is observed (Kulminski et al., 2008).
Among the deficits which characterize people who are frail are those which can be considered as analogous to “state variables” in physical systems (Rockwood and Mitnitski, 2007). State variables are quantifiable and integrate information across a range of sub-systems. A common example is temperature, which represents the average kinetic energy of the molecules of a system. In medicine, the vital signs of temperature, blood pressure, and pulse represent quantifiable estimates of the clinical state. In this regard, orthostatic change in blood pressure might be a candidate state variable, with OH presenting the type of system dysregulation seen in frailty. In this way, measuring OH could represent a means of quantifying loss of physiological reserve (Rockwood et al., 2010). However, measurement of OH requires both supine and standing blood pressures, which may be most challenging in the very frail older people in whom it may be most relevant.
The objectives of this study were: to evaluate the feasibility of measuring change in blood pressure in older adults, and; to evaluate OH in relation to age, frailty, systolic hypertension, and mortality. We also aimed to compare the deficit accumulation approach and the frailty phenotype approach in relation to OH.
Section snippets
Subjects
Data were from the 2nd clinical examination of the population-based Canadian Study of Health & Aging (CSHA-2), conducted in 1996–1997 (CSHA, 2000). Of 2305 people studied, complete data were available on 1347 people, with a mean age of 83.2 years (SD = 6.4 years). The examination included a history that was obtained from either the participants or a knowledgeable informant. The examination also used information from records, where they were available.
Data collection
Participants were assessed with a standardized,
Results
Of 2305 people examined in the second wave clinical examination, complete blood pressure data were available on 1347. People with OH tended to be frailer and were more likely to be female, as shown in Table 1.
Frailty was common in this cohort. Considering the phenotypic definition, of the 1347 people with OH data, 636 (47.2%) were considered “robust” on the phenotypic frailty scale and had a mean FI score of 0.10 ± 0.07, 407 (30.2%) were considered “pre-frail”, with a mean FI score of 0.20 ± 0.10,
Discussion
This work addresses one of the candidate deficits that might define physical aspects of frailty in older adults, as we have recently done in the same dataset with regard to mobility and balance (Davis et al., 2011). Here, we evaluated the feasibility of measuring a change in blood pressure in frail older adults, and the relationship between OH, age, frailty, systolic hypertension, and mortality. The feasibility of measuring OH should not be assumed; data were missing in an important proportion
Conflict of interest statement
KR reports applying for funding to commercialize a version of the FI based on a CGA.
Acknowledgements
The data reported in this article were collected as part of the CSHA. The core study was funded by the Seniors’ Independence Research Program, through the National Health Research and Development Program (NHRDP) Project 6606-3954-MC (S). Separate support for enriching the study of frailty in CSHA-2 came from NHRDP Project 6603-1417-302 (R). Funds for the present analysis came from the Fountain Innovation Fund of the Queen Elizabeth II Health Sciences Foundation and the Canadian Institutes of
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