Intensive blood pressure control has no impact on mobility in elderly

In elderly hypertensive patients, treating to a systolic blood pressure <120 mm Hg (vs <140 mm Hg) was not associated with changes in gait speed or mobility limitations in the Systolic Blood Pressure Intervention Trial (SPRINT).

“Intensive blood pressure control does not appear to have an important effect on short-term gait speed decline among older adults,” Dr. Nicholas Pajewski of Wake Forest School of Medicine in Winston-Salem, North Carolina, and colleagues note in their JAMA Internal Medicine report, online February 6.

SPRINT showed that targeting a systolic BP of <120 mm Hg has benefits on cardiovascular illness and death in hypertensive adults aged 50 and older with no history of type 2 diabetes or stroke. This benefit was seen in adults 75 and older and, in exploratory analyses, in those with frailty or slow gait speed. But whether intensive BP control affects physical function outcomes is unknown, the researchers say.

To investigate, they compared the trajectory of gait speed decline and new mobility limitation in the subgroup aged 75 and older randomized to intensive and standard BP control arms of SPRINT. They had gait speed data for about 1,300 subjects in each study arm and mobility data for 1,250 in each arm.

During a median follow-up of three years, there were no between-group differences in decline in gait speed. In both groups, the average rate of gait speed decline was about 0.08 m/s across follow-up.

In addition, intensive BP treatment was not associated with changes in mobility limitation compared with standard treatment.

“These findings were robust to statistical attempts to account for missing data and the competing risk for death,” the researchers say. “The effect of intensive lowering of BP on the change in gait speed was consistent across subgroups defined by age, sex, race, systolic BP, history of chronic kidney disease, and history of CVD.”

The researchers found “modest evidence” of a differential effect on physical quality of life (QOL), such that intensive BP lowering appeared to be associated with a slower rate of decline in gait speed in those with better physical QOL, whereas among those with worse physical QOL, intensive BP lowering appeared to be associated with a faster decline in gait speed.

“Participants with preserved physical QOL may have gained additional benefit from intensive treatment. However, these findings should be interpreted with caution because the effect size was modest and did not reach statistical significance in either group,” the researchers say.

Summing up, they say, "SPRINT is, to our knowledge, the first large-scale randomized clinical trial of BP control to report results concerning gait speed as an outcome. The benefits of intensive BP lowering on cardiovascular prevention and mortality do not appear to affect short-term mobility.”

The researchers note that SPRINT was stopped early owing to a significantly lower rate of the primary composite outcome (risk of death or CVD events) in the intensive-treatment group, meaning they couldn't look at the long-term effects of intensive BP lowering on gait and mobility outcomes.

“This early termination may have limited the trial’s power to detect differences in gait speed or mobility limitation,” they note.