Patient Safety Tip of the Week
August 14, 2012
Gait Speed: A New Vital Sign?
Last week (see our August 7, 2012 Patient Safety Tip of the
Week “Cognition,
Post-Op Delirium, and Post-Op Outcomes”) we noted that in the pre-op
evaluation we get a lot more bang for the buck doing simple screening for three
risks: obstructive sleep apnea (OSA), frailty, and cognition/delirium. An
otherwise excellent recent review on the preoperative medical consultation (Rivera
2012) briefly discusses OSA but does not even mention screening for frailty
or cognitive dysfunction at all. We had
previously cited the work of Robinson and colleagues (see our November 2011
What’s New in the Patient Safety World column “Timed
Up-and-Go Test and Surgical Outcomes” and our August 9, 2011 Patient Safety
Tip of the Week “Frailty
and the Surgical Patient”) in predicting postoperative complications based
on frailty measures (Robinson
2009, Robinson
2011).
Several more recent
papers in the surgical literature have demonstrated that measures of frailty
reliably predict post-operative morbidity and mortality. One study (Tan
2012) found that the Fried index (see below) predicted morbidity in elderly
patients undergoing colorectal cancer resection even in patients whose
comorbidities were already optimized. Another (Farhat
2012), using a modification of the Canadian Study of Health and Aging
Frailty index, showed that as the modified frailty index increased there were
associated increases in wound infections, various other adverse outcomes, and
mortality. A third study (Nutt
2012) showed that a simple shuttle walk test performed pre-operatively
predicted morbidity and mortality after elective major colorectal surgery.
Gait speed has been an integral part of frailty assessments since Fried et al developed their well-known Frailty Index (Fried 2001). About a year ago a study (Studenski 2011) correlated gait speed with survival in older adults, demonstrating that survival predicted by age, sex and gait speed was at least as good as survival predicted by age, sex, chronic conditions, smoking history, blood pressure, BMI and hospitalization.
While gait speed is obviously impacted by orthopedic, rheumatological and neurological conditions affecting the lower extremities, it is impacted much more globally by multiple organ systems (cardiac, respiratory, CNS, etc.) and therefore is a good measure of overall functional status and/or physiological reserve.
This year there has been a renewed interest in research on gait speed and a variety of outcomes. And researchers have begun to look at not just a single measurement of gait speed but also at changes in gait speed over time and variability of gait speed. A recent study (Dodge 2012) demonstrated that both gait speed and the trajectory of variability in gait speed may predict mild cognitive impairment. They studied independently living patients aged 70 and older and looked at measures of cognitive function and gait speed over time. They separated patients into fast, moderate and slow groups based on measurements of gait speed taken unobtrusively in patients in their homes. Those in the fast and moderate groups had a slight decline in gait speed over time whereas those in the slow group had a more rapid decline in speed. Patients with mild cognitive impairment were 9 times more likely to be in the slow category and 5 times more likely to be in the moderate group. Moreover, they found significant day-to-day fluctuations in gait speed and suggest that monitoring gait speed variation over time may be much more valuable than a typical one-time assessment on an office visit. Indeed, several more studies presented at the 2012 Alzhiemer’s Association International Conference (Cassels 2012) have expanded on this work. One study from Switzerland showed that cognitive function declined as gait speed or its variability declined over time. Another looked at the impact of dual tasks on gait speed. Those with cognitive impairment had slower gaits during dual tasks (such as counting backwards or naming animals) than they did when walking normally. (We pride ourselves at being able to pick out those drivers on the highway who are talking on cell phones. They are the ones who drive fast, then slow, the fast again. Variability in speed is their hallmark. Try it sometime. Wonder if they have cognitive dysfunction, too!).
And there may be more importance in identifying slow gait speed in the elderly. A new study (Odden 2012), using data from NHANES surveys, looked at correlation between blood pressure and gait speed and survival. They found that among fast walkers high blood pressure was associated with higher mortality. For slower walkers there was no association between blood pressure and mortality. But for those who could not complete the walking test, there was an inverse relationship between blood pressure and mortality, i.e. those with higher BP lived longer. Though they speculate on the mechanisms, they note that identification of frailty through gait speed perhaps should lead to less aggressive management of blood pressure. Further research in needed in this area but the findings are nevertheless very interesting.
Gait speed is easy to measure, inexpensive, and not time-consuming. An incredible amount of predictive information can come from such assessment.
References:
Robinson TN, Eiseman B, Wallace JI, et al. Redefining Geriatric Preoperative Assessment Using Frailty, Disability and Co-Morbidity. Annals of Surgery 2009; 250(3): 449-455, September 2009
Robinson TN, Wallace JI, Wu DS, et al. Accumulated Frailty Characteristics Predict Postoperative Discharge Institutionalization in the Geriatric Patient. J Am Coll Surg 2011; 213(1): 37-42, July 2011
http://www.journalacs.org/article/S1072-7515%2811%2900089-5/abstract
Studenski S, Perera S, Patel K, et al. Gait Speed and Survival in Older Adults. JAMA 2011; 305(1): 50-58.
http://jama.jamanetwork.com/article.aspx?articleid=644554
Fried LP, Tangen CM, Walston J; et al. Frailty in older adults: evidence for a phenotype. J Gerontol A Biol Sci Med Sci. 2001; 56(3): M146-M156
Odden MC, Peralta CA, Haan MN, Covinsky KE. Rethinking the Association of High Blood Pressure With Mortality in Elderly Adults. The Impact of Frailty. Arch Intern Med. 2012; 172(15): 1162-1168 published online July 16, 2012
http://archinte.jamanetwork.com/article.aspx?articleid=1217205
Dodge HH, Mattek NC, Austin D, et al. In-home walking speeds and variability trajectories associated with mild cognitive impairment. Neurology 2012; 78: 1946-1952
http://www.neurology.org/content/78/24/1946.abstract
Cassels C. Walking Irregularities a Harbinger of Cognitive Decline? Medscape Medical News July 15, 2012
http://www.medscape.com/viewarticle/767453
Nutt CL, Russell JC. Use of the pre-operative shuttle walk test to predict morbidity and mortality after elective major colorectal surgery. Anaesthesia 2012; 67: 839–849
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2044.2012.07194.x/abstract
Tan K-Y, Kawamura YJ, Tokomitsu A, Tang T. Assessment for frailty is useful for predicting morbidity in elderly patients undergoing colorectal cancer resection whose comorbidities are already optimized. Amer J Surg 2012; 204(2) 139-143
http://www.americanjournalofsurgery.com/article/S0002-9610%2811%2900656-8/abstract
Farhat JS, Velanovic V, Falvo AJ, et al. Are the frail destined to fail? Frailty index as predictor of surgical morbidity and mortality in the elderly. Journal of Trauma and Acute Care Surgery 2012; 72(6): 1526-1531
http://www.patientsafetysolutions.com/