Abstract
Diastolic blood pressure declines after age 50 such that older adults commonly have a diastolic pressure well below the optimal range of 80-90mmHg, resulting in increased risk of all-cause mortality, cognitive impairment, heart disease, and cancer. The cause of the age-related diastolic pressure decline is not well understood. We propose diastolic blood pressure declines with age primarily due to decreased venous return resulting from soleus muscle atrophy. Neuro-rehabilitation of the soleus muscles in older adults has the potential to improve venous return thereby enhancing resting cardiac output, and correspondingly, optimizing diastolic blood pressure. In a repeated measures prospective clinical trial, subjects (N=25, age 75.7±7.2 years) underwent daily, non-invasive, soleus muscle neuro-rehabilitation for six months, initiated through plantar nerve modulation. Average soleus muscle fatigue strength increased more than 2x over the six months, resulting in an average 0.4 L/min/m2 increase in resting cardiac index (range 0.1-0.8 L/min/m2; p=0.003). This enhanced cardiac output led to an average rise in resting diastolic blood pressure of 8mmHg, from 63.5mmHg to 71.5mmHg (p=0.001) in subjects not undergoing hypertension therapy. Extrapolation indicated that optimal (>80mmHg) diastolic blood pressure could be achieved, on average, with approximately one year of daily neuro-rehabilitation. These results provide confirmation that decreased venous return resulting from soleus muscle atrophy plays a significant role in the age-related decline in diastolic blood pressure, though overmedication and polypharmacy appear to also play significant roles. These results provide support for neuro-rehabilitation of the soleus muscles as a convenient and non-invasive means to create substantial clinical benefits in older adults by reducing the numerous health complications arising from chronically low cardiac output and diastolic blood pressure.