Walking speed could explain high BP and mortality link in elderly

By Sarah Guy, MedWire Reporter

Elderly individuals with high systolic blood pressure (BP) who walk quickly have a higher mortality rate than their counterparts who walk more slowly, show US study results.

Strikingly, participants in the study who did not take the walking test because they refused, it was not safe to, or they had physical limitations (among other reasons) had a lower mortality risk the higher their diastolic BP, report the researchers.

Together, the results show that "walking speed appears to be a simple measure to explain the differential association of high BP and mortality in older adults," remark Michelle Odden (Oregon State University, Corvallis) and colleagues in the Archives of Internal Medicine.

The study cohort included 2340 individuals aged 65 years and older with BP data recorded in the nationally representative National Health and Nutrition Examination Survey, of whom 589 had died by 2006, the end of the study. Levels of 140 mm/Hg (systolic) or higher and 90 mm/Hg (diastolic) or higher were considered to be elevated.

In all, 56% of participants had a walking speed of 0.8 m/s (1.8 mph) or faster, while 34% walked at a pace under 0.8 m/s, and 10% of the cohort did not complete the 6 m walking test.

After adjusting data for potentially confounding factors such as age, gender, race, education, and smoking status, the researchers found that fast walkers with elevated systolic BP were 35% more likely to have died by the study end than those with BP in the normal range.

The team reports no association between elevated systolic BP and mortality in slow walkers, nor between high diastolic BP and mortality in fast walkers.

Participants who did not complete the walking test and who had elevated diastolic BP had a significantly lower mortality rate compared with those who had low diastolic BP, with mortality reducing by 33% with each 10 mm/Hg increase above the norm in this group, report Odden et al.

This apparently protective association could indicate that elevated BP is necessary to maintain perfusion of the vital organs in older, frail adults, the team concludes.

In an associated commentary, James Goodwin (University of Texas Medical Branch, Galveston) remarked that Odden and team's results not only demonstrate the utility of gait speed in understanding the health of the elderly, but also give "a better understanding of the complexities of BP in old age."

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